A PRIVATE island estate with a rich history and natural heritage in the Firth of Clyde is up for sale.

It was an early island monastery, a target of Viking raids, popular with smugglers (so rumour goes) and a World War Two training ground – and the remains of a Bronze Age woman were found there.

Now the 660-acre island of Inchmarnock – complete with an in-hand farm, native woodland, sportings, a small private harbour, its own bespoke ferry and almost five miles of coastline in the Firth of Clyde – is for sale.

The sale includes Port House, an attractive four-bedroom renovated waterfront property 2km across the water at Straad on the west coast of Bute, currently used as a holiday home. With its own slipway and overlooking Inchmarnock Island, it is just 10 minutes from the seaside town of Rothesay.

The estate has been transformed since the current owners bought it in 1999 – at which point it had been uninhabited for 25 years – and it also comprises a productive in-hand farm with a fold of pedigree Highland cattle and a Highland cross Beef Shorthorn commercial suckler beef herd as well as a wealth of sporting, leisure and recreational opportunities.

Among the facilities and machinery offered for sale as additional purchases is The Marnock, a bespoke ferry commissioned by the owner to transport livestock and machinery between Inchmarnock and Bute, and the estate RIB.

Inchmarnock was once home to 41 residents but the final permanent resident, a Bute farming tenant, left the island in 1986.

Diane Fleming, sales agent for Strutt and Parker in Edinburgh, 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.

“We expect significant interest from national and international buyers.”