He is one of Scotland’s leading business figures whose “romantic idea” to buy some land ended up in a 20-year restoration project on a small Scottish island.

Lord Smith of Kelvin bought Inchmarnock, in the Firth of Clyde, in 1999 after the island was abandoned and forgotten for decades and left to fall into disrepair.

He has now returned the beauty spot to its former glory, with green pastures and grass leys now playing home to a cattle farm - but the prolific businessman has decided it is time to sell it on.

On the market for £1.4 million, the island has its own private harbour and bespoke ferry service, while the listing also includes Lord Smith’s holiday home on Bute which overlooks Inchmarnock.

Speaking to The Herald, the peer, originally from Maryhill in Glasgow, told how he has had many happy memories on the island, but the time has come to let it go.

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“I’ve had it for 20 years,” he said, “When I bought the thing, the island hadn’t been inhabited for around 30 years, but with the help of locals we’ve brought it back to life.

“I’m 75 in a couple of weeks’ time and I’m kind of consolidating things, so the time is now to sell it on.

“It’s a beautiful island, I’ve camped across there with my grandchildren and we have many happy memories and great photographs of our time there.

“I’m a wee bit emotional, you obviously get attached, but it’s going to have to happen at some point and it seemed an appropriate time.

“I’ve had 20 years of great fun watching the thing developing.”

Inchmarnock, which is being sold by estate agents Strutt and Parker, is 2.5 miles long, half-a-mile wide and has 4.75 miles of coastline.

It also has its own in-hand farm, native woodland, a small private harbour and bespoke ferry.

The property on Bute - the Port House - is a four-bedroom house which also has a boat shed and slipway on its grounds to allow access to the island.

Lord Smith, who has led numerous private equity business and chaired BBC Children in Need and the Glasgow 2014 Commonwealth Games committee, said that, in the late 90s, he had decided to buy some land when Inchmarnock came up for sale.

“I’ve always liked open spaces,” he said. “My father came from Milngavie and I used to go out there and run around the moors and things like that, and I fancied the idea of having some land somewhere.

“I’ve been relatively successful so I was in a position to be able to do that when suddenly this island came up.

“It was uninhabited, totally overgrown, when we first went across there were chest-high briars, you couldn’t really move around the island.

“But it was a romantic idea to own it, and the wee holiday home on Bute.”

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Laughing, he added: “For the first few years I could look out to the island and watch the pound notes evaporating. It’s cost quite a wee bit of cash to bring it back to proper farmed land.”

Inchmarnock is still uninhabited by humans, but is now home to around 230 cows, who are fed with crops grown on the island.

Lord Smith has also helped to uncover some of the island’s history by commissioning a five year archaeological project.

The project has uncovered an array of artefacts, including carved stones and the largest collection of inscribed slate in the British Isles.

A book detailing the finds was published and tells the island’s story from Viking raids in the 8th century to being used as a training ground in preparation for the D-Day landings.

It also details the discovery of a local Bronze Age woman, the Queen of the Inch, which dates back around 3,500 years.

She was discovered in a stone cist on the north east of the island in 1960s and is now part of an exhibition in the National History Museum in Rothesay.

Lord Smith said: “The island is rich in history so I instructed private archaeologists to look at it and for years they went over and did research.

“That has resulted in a book being published on Inchmarnock - a big thick, scholarly tome.

“There’s a lot of history here and now it’s all documented in this book.”

Diane Fleming, sales agent for Strutt & Parker in Edinburgh, said she expects significant interest in the island.

She said: “Inchmarnock is a stunning island rich in possibility.

“There is already a successful farming enterprise and a lovely family home on the nearby shore of Bute but there is significant potential to build up the sportings, develop the existing residential offering and to capitalise on the various amenities offered by the island such as the native woodland, watersports and fishing.

“A Scottish island embodies the romance many people associate with the country’s prime estates and farms.

“Inchmarnock is stunning with great heritage and is a peaceful and secluded haven, yet it is relatively accessible from Scotland’s central belt.”