Lundy lies in splendid isolation off the North Devon coast
The National Trust picked up a bargain when it bought Lundy for £150,000 in 1969.
The trust purchased the tiny island thanks to a donation from Sir Jack Hayward, who is also known as the owner of Wolverhampton Wanderers Football Club.
It has proved to be money well spent. Forty years on, and Lundy - which sits some 10 miles off the North Devon coast - is thriving economically and environmentally.
BBC Devon's Lundy gallery
As part of the purchase, the Landmark Trust took over the day-to-day management of Lundy and between them, the two charities have run the island with its unique environment in mind.
For such a small place - Lundy is three miles long and half a mile wide - the island is big when it comes to its environmental importance.
The waters around Lundy are England's only Marine Nature Reserve and the UK's first No Take Zone - where fishing is banned to protect corals and other marine life.
This is the only place in the UK where you can find all five British species of shallow water cup coral.
The waters around Lundy are a delight for divers
On the island itself, the cliffs are home to the largest seabird colony in the South West, with puffins, kittiwakes, guillemots, razorbills, shags, fulmars and Manx shearwaters - Lundy provides the only nesting site in England for Manx shearwaters.
Around 140 different species of birds are recorded on Lundy each year, with up to 35 species nesting on the island.
And if you visit Lundy, there's every chance you'll spot an Atlantic grey seal basking in the coastal waters.
The flora and fauna is another reason why around 20,000 visitors head to Lundy each year. Most people go for the day, travelling by the island's very own supply ship, MS Oldenburg.
The islands's 23 holiday accommodation buildings - including a lighthouse and an old castle - are quickly booked up by people wanting to get away from it all.
There is a pub, a working farm, fantastic church, and a post office/shop, selling Lundy's unique stamps.
Apart from that, it's all open spaces and fresh air! Rising to 400ft above sea level, Lundy is criss-crossed by a network of 13,000ft (4,000m) of granite drystone walling.
This is a car free island (apart from the essential work vehicles), and the island generates its own electricity, which is usually switched off at midnight to conserve supplies.
The Oldenburg is Lundy's link to the mainland
And all the jobs are done by the 26 staff on the island - including the fire and rescue duties.
This way of managing the island has helped to protect its uniqueness, according to the two trusts.
Director of the Landmark Trust, Peter Pearce, said: "It is only thanks to our 40 year partnership with the National Trust that the many thousands of people from all walks of life who visit Lundy and stay there each year can still do so now.
"The Landmark Trust counts its work on Lundy as one of its greatest ever achievements."
Fiona Reynolds, director general of the National Trust, hailed the 40-year partnership as a great success. She added: "Above all, thanks to the careful management of the Landmark Trust, it has the most amazing atmosphere.
"Its sheer cliffs and springy turf, wild winds and shady suntraps, characterful houses, the Oldenburg and the friendly pub and shop all add up to an essence that is Lundy."