Britain's farmers are being urged to seek hidden treasure.

But they won't be needing metal detectors and spades to unearth the sort of treasure that Strutt & Parker, the rural business advisers, are talking about.

In the latest edition of Land Business, Strutt & Parker argue that almost every farm or estate has at least one underused asset that could be put to more profitable use. The big challenge kies in spotting it.

Ralph Crathorne, a partner who chairs the firm's land research group, explains: "These days, hidden treasure on a farm or estate really can come in all shapes and sizes.

"Sometimes, finding it is far from difficult: that pretty little field that got cut off by the bypass, for example, is obviously perfect to sell for house-building."

But most hidden treasure, he warns, would be harder to spot. It could be that old chalk pit where antisocial vneighbours dump their fridges, or the overgrown set of foundations where your grandfather knocked down an old house that had got too expensive to repair. And what about that strip of land between the drying shed and the road that's too narrow to park the tractor on?

"It's all about getting out, walking your land and thinking laterally," says Mr Crathorne, adding that it is always advisable to take a second opinion along.

"It doesn't have to be a land agent, but it does need to be someone with up-to-date knowledge of the local property market, a good understanding of the planning system and an ability to see things as they could be, rather than as they are."

They will be able to tell landowners whether they might get planning permission for a couple of cottages in that old chalkpit, or, failing that, whether it might be a good place to hide away some anti-social industrial use, such as a sawmill or recycling unit.

They'll also be able to explain why those old foundations could make it much easier than expected to get planning permission to build on the site and how much annual rent a mobile telecoms company might be willing to pay for a mast on that narrow strip by the drying shed.

Just as importantly, says Mr Crathorne, they can also tell you what you can't do. "Only a few years ago, every other farmer seemed to have plans to develop a golf course. Now we all have to be a lot more imaginative."

Conversely, what was impossible a few years ago now just might be achievable. "Getting residential planning permission for greenfield sites used to be just a fantasy for most landowners.

"But now, with housebuilding starts at record lows and the Government miles behind its own targets, it really could be worth taking another look."

Even a couple of acres of land with residential planning permission can turn its lucky owner into a millionaire. But most hidden treasure will produce far more modest returns.

"In these tough times for the rural economy, every acre has to work harder to earn its keep," concludes Mr Crathorne.

"That's why we believe farmers and landowners should carry out this sort of exercise every year.

"Markets, values and planning criteria all change - and, who knows, one day you could find yourself sitting on something really valuable."