Flat Holm Island

We are pleased to announce that Flat Holm is reopening to visitors from July 2021.

We look forward to welcoming you to the island soon!

Rich in Wildlife – Steeped in History

Flat Holm has a unique island character, with a sense of wilderness, remoteness and isolation, and extensive views from and across the Island to the coasts of England and Wales. Less than half a mile wide, the tiny Island is an intriguing hidden jewel in the Bristol Channel. Flat Holm is designated a Site of Special Scientific Interest and Local Nature Reserve. The Flat Holm Project conserves the Island’s natural and cultural features, from maritime grassland to Victorian barracks, from seabird colonies to wartime bunkers.

…Come and explore

Flat Holm Island is steeped in history with the earliest known visitor to Flat Holm being St Cadoc. He made frequent visits to the island in the late 6th century for periods of tranquil meditation, especially during Lent. During the 18th century, the island’s location made it an ideal base for smuggling. It has been alleged that an old mine shaft on the north side of the island connects with a series of natural tunnels, and a concealed exit to the sea. Although Flat Holm is in full view of both the Welsh and English coasts, customs authorities were powerless to act as they had no boat to take them to the island. According to tradition, a small cave in the east cliff at Flat Holm was used for the storage of contraband, mainly tea and brandy.

On 13 May 1897, a 22-year-old Italian inventor named Guglielmo Marconi, assisted by a Cardiff Post Office engineer named George Kemp, transmitted the first wireless signals over open sea from Flat Holm to Lavernock Point near Penarth. Having failed to interest the Italian government in his project, Marconi brought his telegraphy system to Britain. He erected a 34m high transmitting mast on Flat Holm as well as a 30m receiving mast at Lavernock Point. The first trials failed, but on 13 May the mast was raised to 50m and the signals were received clearly. The message sent by Morse Code was “Are you ready?”; the original paper Morse slip, signed by both Marconi and Kemp, is now in the National Museum of Wales.

Images by: Gareth Johns

View full history

Flat Holm is part of the Parish of St Mary’s in Cardiff and inextricably linked to Cardiff’s history.

The axe head found on the island is believed be from the late Bronze Age, 900 to 700 BC. In the absence of any other archaeological evidence it is not known if the island was settled at that time. The Anglo-Saxons called the island “Bradanreolice”, and Steep Holm “Steopanreolice”, confirming the religious associations of the islands, as ‘reolice’ derives from an Irish word meaning churchyard or graveyard.

The earliest known visitor to Flat Holm was St Cadoc. He made frequent visits to the island in the late 6th century for periods of tranquil meditation, especially during Lent. Gildas, Barruc and Gwalches, all disciples of St Cadoc, are known to have visited Flat Holm. Gwalches and Barruc were returning from Flat Holm, where they had been sent by St Cadoc to retrieve a book forgotten on a previous visit, when the boat overturned and they were drowned. Barruc’s body was washed ashore and interred on Barry Island, whilst the body of Gwalches was carried to the Island of Echni, and buried there.

In the year 918, following their defeat by the Saxons at Watchet, Danish invaders took refuge on the islands of Steopanreolice and Bradanreolice, though for how long is uncertain. From the Anglo Saxon Chronicle:

“918 – In this year a great naval force came over here from the south of Brittany, and two earls, Ohter and Hroald with them. And they went west round the coast so that they arrived at the Severn estuary and ravaged in Wales everywhere along the coast, where it suited them… Yet they stole inland by night on two occasions – on the one occasion east of Watchet, on the other occasion at Porlock. Then on both occasions they were attacked, so that few of them got away – only those who could swim out to the ships. And then they remained out on the island of Flatholm until they became very short of food and many men had died of hunger because they could not obtain any food. Then they went from there to Dyfed, and from there to Ireland; and this was in the autumn.”

Another entry in the Anglo-Saxon Chronicle states:

“1067 – And Gytha, Harold’s mother, and many distinguished men’s wives with her, went out to Flatholme and stayed there for some time and so went from there overseas to St Omer.”

The name of Holm or Holme derives from the Scandinavian for river island and although the Danes may not have stayed on either island for long they certainly used both Flat Holm and Steep Holm as navigational aids during attacks along the Severn estuary.

The Lighthouse

The first light was kindled on 1 December 1737. The light consisted of only a coal-fired brazier, the coal having to be carried by the keepers from the stores to the top of the tower. The light consumed large quantities of coal and 25 tonnes were landed on the island each month.

In 1819 Trinity House agreed to take over the tower from William Dickenson for the remainder of his lease and undertake the alterations.

The massive circular stone tower was adapted to make a suitable base for a lantern enclosing an oil-burning lamp. This new fixed white light was first shown on 7 September 1820. The lantern was raised a further 5 feet in 1825 and a new 14 foot diameter lantern installed in 1867, which remained until the light was converted to electricity in 1969. In 1881, the light was converted to occulting by the installation of a clockwork mechanism and now has a characteristic pattern of white and red group flashing three times every ten seconds, and a range of 21 miles. In 1997 the light was converted to run on solar power.

The Fog Horn Station

In 1908 a foghorn station was built. The powerful compressed air fog signal was installed in one building, whilst a cottage provided the keepers with extra accommodation. In 1929 the lighthouse became a rock station, the keepers previously having lived with their families in two cottages at the base of the lighthouse tower. These buildings then became redundant and were demolished. In more recent years the lighthouse was manned by two sets of three keepers, each working one month on the lighthouse followed by one month ashore.

An Island Fortress

In 1860 the Royal Commission recommended that Flat Holm was to form part of a “strategic coastal defence system for the Bristol Channel”, which included Brean Down, Steep Holm and Lavernock. Preparations for construction of the fortress on Flat Holm began in 1865, and it was completed in 1869. Despite the millions spent, an attack never occurred.

Due to the relatively low and exposed terrain, Moncrieff Disappearing Carriages were installed on Flat Holm. Each of these carriages carried a 7” Rifled Muzzle Loading (RML) gun, the last of the muzzle loaders, and was mounted in circular or U-shaped pits constructed of limestone and bricks. The recoil caused by the firing of the 115-pound shell forced the gun downward into the gun-pit. In the down position the gun was reloaded and then with the aid of a large counterweight, raised ready for firing once more. Not only was it difficult for an enemy ship to locate and range its guns on such a battery, but also the crews were protected within the pit, whilst servicing the gun. However, the guns were only fired in tests and their potential was never fully realised.

Nine of these guns were installed on Flat Holm in four batteries: Lighthouse, Well, Farmhouse and Castle Rock Batteries. The four batteries were all provided with magazines. Unfortunately, the carriages were comparatively easy to dismantle and have subsequently been removed, but most of the guns remain on the island, despite past efforts to salvage them for scrap, albeit in some cases without their muzzle ends.

Lighthouse Battery on the highest part of the island was integrated with defences enclosing the barracks, administrative buildings and lighthouse. The fortified area provided a fall back defence in the event of an enemy landing. The deep rock cut ditch exploited a natural geological fault and was protected by a strong parallel rampart. The battery and the Trinity House land around the lighthouse occupy the southern part of the fortified area. To the north, the barrack block, dated VR 1869, administrative buildings and a secure store surrounded a parade ground. These provided quarters for the 50 soldiers needed to man the four batteries, but only a Master Gunner and five gunners were ever stationed on the island. An impressive tiled water-catchment area was constructed, sloping towards a large underground water-storage tank. This tank is still in use today to collect rainwater to provide the island’s water supply.

Messages across Water – Guglielmo Marconi

Having failed to interest the Italian Government, 22-year-old inventor Guglielmo Marconi brought his telegraphy system to Britain. He was given an introduction to William Preece, a Welshman, who was a major figure in the field and Chief Engineer of the General Post Office. Having successfully demonstrated his spark wireless telegraphy system on Salisbury Plain in March 1897, he came to Flat Holm, with his assistant George Kemp in May.

Early in May 1897, Kemp and Marconi successfully transmitted the first ever wireless messages to go over the sea, from Flat Holm to Lavernock Point, witnessed amongst others by Professor Slaby, on behalf of the Kaiser. The morse slip, “Are you ready?” was sent on 13 May, signed by Signor Marconi and George Kemp.

Cholera & the Isolation Hospital

In 1883, Flat Holm became used as an isolation hospital to protect the mainland against a cholera epidemic.

In 1892, after a serious outbreak of cholera in Hamburg, five infected vessels were discovered and moored off Flat Holm. Patients were removed and taken to Flat Holm’s hospital. The following year cholera broke out again and two more patients were taken to the hospital. The small building was proving to be insufficient and it was decided that a more substantial hospital was needed. In 1896 a new hospital was built. The main building consisted of two six-bed wards, whilst the converted building was improved to provide four extra beds. A laundry and a wooden crematorium were also constructed.

In 1935 the Ministry of Health condemned the building.

World War II

The fortification of Flat Holm started in spring 1941 and the main construction of the gun positions continued throughout 1942.

Over 350 soldiers were then stationed on Flat Holm. Two batteries under Anti-Aircraft (AA) Command were established. Both consisted of two heavy, 4.5 inch AA Mark 2 guns, a command post, and were flanked by two searchlights. Bofor and Lewis guns augmented the AA armament.

Incorporated into the design of the South Battery was the now nicknamed “Benger Goalpost”. Major D Benger, who commanded 146 Coast Battery, was worried by the proximity of his Number 2 Gun to the Lighthouse. There was considerable danger that the gun might blow the top off the tower. He had a frame of 2” steel piping erected, which forced the gun to be raised, thus avoiding the danger.

A narrow gauge railway, unusually of World War I German construction, used diesel locomotives and wagons to convey ammunition, materials and provisions across the island.

In the centre of the island there was a Radar platform on which sat the mobile radar receiving cabin, surrounded by a false horizon of wire netting. Full use was made of the old Victorian Barracks, and whilst one ward of the Cholera Hospital was turned into a NAAFI, the other was used as a cinema and concert hall, complete with projection room. Films were shown almost every fortnight, and concert parties held once a month. The farmhouse was used as the Officers’ Mess.

Flat Holm became non-operational in December 1944. In 1945/6 German prisoners of war removed most of the equipment from the military occupation.

Trips are available all year round to visit Flat Holm, from day trips to longer stays. There are pre-organised RIB boat trips to the island that depart from Cardiff several times a month, and can take up to 12 passengers on each RIB. The trips allow you up to three hours on the island, depending on tide times. Alternatively, you can tailor your own visit if you have a large group or would like to stay for a long day or overnight.

Day Visits

A short day visit to Flat Holm provides up to three hours on the Island and offers a unique opportunity to see Flat Holm’s conservation, wildlife and historic buildings.

How to book

Day sailings to the Island can be booked with the following operators:

Website Telephone
Cardiff Sea Safaris visitflatholm.co.uk 029 2048 7663
Bay Island Voyages bayislandvoyages.co.uk 07393 470476


A landing fee of £5.00 for adults and £2.50 for children is payable to the warden upon arrival on the island.

Please contact boat operators regarding boat fares.

Overnight Stays / Residential Visits

You can tailor your own visit if you have a large group or if you would like to stay for longer than a day.


Overnight Stays / Residential Visits

  • Dormitory accommodation is available in our farmhouse field centre, which can sleep up to 24 people (two, 10 and 12 bedded rooms).
  • Camping will be available in the farmhouse paddocks when the dormitory accommodation is fully booked (tents not provided).
  • The Grade II Listed Fog Horn Cottage has been converted into a self catering cottage, offering a stylish double bedroom, twin bedroom, lounge with double sofabed, two toilet/shower rooms, fully equipped kitchen, and dining room with table and chairs for six. The cosy cottage also boasts a biomass boiler for heating, front and rear entrance, and private garden with stone BBQ and inspiring views.

Furnished in partnership with John Lewis Cardiff, this is the ideal place to get away from it all.

How to book

To book a residential visit please contact:

The Flatholm Booking Office,
Cardiff Harbour Authority,
Queen Alexandra House,
Cargo Road,
Cardiff Bay
CF10 4LY

Tel: 029 2087 7912

Email: flatholmproject@cardiff.gov.uk

Fax: 029 2087 7901


Landing Fee          

Adult £5.00
Child £2.50


Residential Visits:

Adult £19.00 per night
Child £16.00 per night


Camping Charge:

Adult £8.00 per night
Child £7.00 per night
Additional Visitor Information

• Adult supervisors are required for children’s groups. The adult to child ratio varies, depending on the type of visit and the age of the children. Please contact us for details.

• Groups are required to supply their own food.

• We do not offer concessionary rates to pensioners, students or unemployed persons.

• Dogs are not permitted on the Island.

Images by: Gareth Johns

Flat Holm Island offers everything you need to explore the exhilarating world of outdoor education. Our aim is to offer Flat Holm Island as an environmental education facility, while still conserving the Island as a nature reserve.

Whether you are looking for an educational day visit or longer we will aim to cater for your needs. Day visits include a general tour of the Island exploring its history and wildlife. Alternatively, if you are looking to complete a certain topic area we can work with you to provide some shorter education based activities. We can also develop a programme of activities for groups staying on the Island for a few nights.

We welcome university groups to carry out their own programme of studies in a range of areas, e.g. biology, marine studies, geology, art.

Please contact us on 029 2087 7912 for more information or to discuss your educational requirements.

The Flat Holm Team manages the Island as a Local Nature Reserve and Site of Special Scientific Interest. The Project conserves the Island’s natural and cultural features, from maritime grassland to Victorian barracks, from seabird colonies to wartime bunkers. There is a field study centre on the Island, which can accommodate residential groups. The Project also runs summer day trips for visitors.

The Team consists of two office-based staff and one island-based Warden.

The Team is supported by up to six volunteers at any time. A commitment of six months is ideal and experience is not necessary. If you are interested in a shorter placement, you should still contact the mainland office.

Interested in volunteering?

If you are interested in volunteering with us, please read the information below and then send your CV and a Covering Letter to: flatholmproject@cardiff.gov.uk


What do volunteers get?

Although we cannot pay volunteers we offer:

· Free board and basic shared accommodation.

· Help with travel expenses.

· External training (First Aid, Lantra Brushcutter and Trimmer).

· On-the-job training (machinery, dry stone walling, tour guiding, education).

· Invaluable experience in a wide range of tasks, with an excellent success rate of volunteers gaining paid employment.


What do volunteers do?

As a volunteer you will be involved in all aspects of the day-to-day running of the Island, including:

· Recording and monitoring wildlife.

· Practical habitat management.

· Leading guided tours for visitors.

· Maintaining listed buildings.

· Stock care and control.

· Leading volunteer work parties.


What do volunteers need?

· Knowledge of environmental/natural sciences or countryside management.

· Enthusiasm.

· Flexibility.

· Communication skills.

· Commitment.

For more information, contact the Flat Holm office on:

Tel: 029 208 77912

Email: flatholmproject@cardiff.gov.uk

Flat Holm Society

Do you have a few hours to spare each week, month or year? Do you have DIY or gardening skills you could offer? Would you like to train to become a tour guide, sit on the committee or help raise funds? Whatever you can offer, we would like to hear from you.

The Flat Holm Society was set up to promote and assist the Flat Holm Project. Society members form working parties, act as guides on the island, raise funds and help with related jobs, as well as supporting social events on the mainland.

Membership of the Flat Holm Society

Each year society members receive details of forthcoming activities and an annual newsletter brings members up to date with society activities. Annual subscription to become a member of the Flat Holm Society is £15.

For further details, contact chair person, Peter Sampson, via the Flat Holm Project Office.

The Flat Holm Society also has its own website:  www.flatholmsociety.org.uk

The Flat Holm Society is a registered charity (Registration No. 1000899).


Flat Holm Booking Office,
Cardiff Harbour Authority,
Queen Alexandra House,
Cargo Road,
Cardiff Bay
CF10 4LY

Tel: 029 2087 7912


About us

Flat Holm Island is managed by The Flat Holm Project which includes a full-time warden and a team of volunteers. The warden lives permanently on the island with about two to three volunteers at any one time. The team works on maintaining, studying and preserving the island, its buildings and its wildlife.

Flat Holm is designated a Site of Special Scientific Interest and Local Nature Reserve. The warden and volunteers conserve the Island’s natural and cultural features, from maritime grassland and Victorian barracks, to seabird colonies and wartime bunkers.

Alongside the Flat Holm Project team is The Flat Holm Society. The society supports the work of the project team by raising funds and providing volunteers. They are a charity that helps protect the wildlife, and historic environment, of Flat Holm.

For further information about the society, please visit: www.flatholmsociety.org.uk


Nature Conservation

Flat Holm is designated a Site of Special Scientific Interest and Local Nature Reserve. The Project conserves the Island’s natural and cultural features, from maritime grassland and Victorian barracks, to seabird colonies and wartime bunkers.

Both the Lesser Black-backed Gull colony and the maritime grassland are considered important for nature conservation. The Island is managed in two separate ways for these features. The north side of the Island is managed for the maritime species and the south side is kept as the gull colony with minimal management.

Management Plan

The Flat Holm Management Plan outlines the important features of the Island. It provides a basis from which to improve the island’s habitats.

In 1982, the Flat Holm Project was established. The aim was to manage Flat Holm as a local nature reserve and to encourage visitor access and opportunities for education.

The Island has a long and varied history, having been used by man since prehistoric times. It was farmed for some 800 years and stopped in 1942. It has been fortified twice, most recently during the Second World War. The Island has many buildings and structures of historic interest, many are listed buildings and scheduled ancient monuments.

Flat Holm’s natural history and geology are both interesting and important. Some of the notable features are:

• Coastal limestone grassland.

• Cliff ledge habitats.

• Wild leek.

• Colony of breeding Lesser Black-Backed gulls.

The following is a list of some of the species that may be seen on the Island throughout the year: Birds: Shelduck, Oystercatchers, Rock Pipits, Finches, Turnstone and Dunlin; Animals: Rabbits, Slow Worms, Common Lizard and Butterflies; Plants: Wild Leek, Wild Peony, Thrift, Rock Sea Lavender, Sea Campion and Bluebells.


The Flat Holm project aims to be a showcase of sustainable technologies. The original power supply consisted of several diesel generators at different properties, which were unconnected.

In 2006/2007, a ‘mini-grid’ between the farmhouse, workshops and the fog horn keeper’s cottage was installed. This is powered by a battery bank charged by two photovoltaic solar arrays, and by a 6kW wind turbine, sited at a redundant telecommunications tower on the high point of the Island. The Island is currently able to generate 90% of its electricity from green sources, reducing its carbon footprint.

The sustainability continues because there is no natural water source on the Island, and as a result rainwater is collected from the roofs of the buildings. This is stored in the underground Victorian water tank and pumped through a UV filtration system.

A solar water heating and biomass boiler provide the Island with most of the hot water and heating that it needs throughout the year. Driftwood collected from the shore is dried out over a year, and used to fuel the boiler, reducing the need to transport wood from the mainland.

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