Set in just under 10 acres of rolling grassland, near Sherborne, Dorset, the Manor House is for sale for a relatively modest £1m. If it were on the open market, the fourbed detached house would probably fetch at least £250,000 more. The catch? The property comes with an agricultural occupancy restriction, which means that the owner must work in farming.

It is one of an estimated 50,000 properties in Britain subject to an agricultural occupancy condition (AOC), a planning restriction introduced after the second world war on any new building proposed by a farmer, to encourage rural housing and keep people on the land.

For that reason, most of these properties are rather plain, modern dwelllings — think 1960s redbrick rather than mellow York stone — but they do sit in attractive countryside.

As the number of people employed in agriculture continues to dwindle, speculators are beginning to snap up these properties. They are gambling on being able to remove the occupancy restriction, because doing so will immediately add 25% to the value of the property.

“Most properties with an agricultural tie are in Lincolnshire, Norfolk, Devon and Dorset,” says Brian Barrow, managing director of Acorus, a rural property service that specialises in the removal of AOCs from properties. The agency, which has offices across the UK, claims to be successful in 70% of cases.

“If you spot a house built in the 1960s or 1970s, surrounded by fields, the chances are it has an agricultural occupancy restriction,” says Barrow. “In many cases, people are living in a house with a restriction but may not know it, they may have long since given up their job in agriculture or inherited a house with a restriction.”

So how do you go about removing such a restriction?

Most planning authorities will require an applicant to prepare a report to demonstrate that a house has been properly marketed for a period, usually one year, at a price that reflects the restriction, thereby giving anybody employed in agriculture an opportunity to buy. Then if you can prove to the local authority that there is no longer a demand for such properties — an increasingly common situation, owing to the dwindling number of farm workers — then it is obliged to lift the restriction.

Alternatively, if you live in the property uninterrupted and undiscovered for 10 years, you can apply to the local authority for a Certificate of Lawful Use. This does not remove the agricultural condition, but does mean you are allowed to stay and can sell the property on the open market. Although the restriction remains in force, it is effectively neutralised by the certificate, so the property should fetch something close to its full market value.

“There is no easy way to value a property with a restriction,” says William Grant, managing director of Fox Grant, a rural estate agency that covers Hampshire, Wiltshire, Dorset and Somerset, who estimates 10% of his sales have an occupancy restriction.

Grant says that councils are not keen to lift the tie, and will look more favourably on stretching the definition of agricultural. In one case, he says, he was unable to have a restriction removed but, after haggling with the planner, he had it widened to include equestrianism and sold the house to a blacksmith.

Barrow has a warning for all speculative purchasers: “When the market is booming, properties with a restriction seem like a good deal,” he says. “But if the market takes a turn for the worse, they are the first to stick. Nobody wants them.”

The Manor House is for sale with Acorus, 0845 601 1047, www.acorus.co.uk; Fox Grant, 08707 745 600, www.foxgrant.com

Artistic reservation

Only artists need apply. If you seek inspiration by the sea, but can’t quite commit to the hermit lifestyle, then Vow Cave Studio is for you. A one-bedroom artist’s studio, set in 3.3 acres of meadowland in the Lamorna Valley, it is just less than a mile from Lamorna Cove and 4½ miles from Penzance.

The studio has a kitchen, an open-plan living room and a galleried bedroom with just about enough room for a double futon. In the summer, you can fling open the doors and windows to the elements, while an oil-fired Rayburn keeps the place warm in the winter.

There is a catch, though. You must be employed as an artist, and the property is limited to 10 months’ residential use a year, according to a restriction imposed by the local planners when it was built a decade ago.

Last on the market four years ago for £175,000, Vow Cave Studio is for sale for £250,000 through Savills, 01872 243 200, www.savills.co.uk

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