LONDON (Bloomberg) — British farmland prices rose at the fastest rate in at least 12 years as rising food and commodity prices encouraged farmers to bid up the cost of land, according to Knight Frank LP.

The average cost of an acre of farmland increased to £4,621 pounds ($9,125) in the first quarter, 34 percent more than a year earlier, according to an index based on valuations by the London-based broker. The index rose 12 percent from the previous quarter, Knight Frank said yesterday in an e-mailed statement.

Wheat prices have more than doubled in the past year, leading global gains for crops and reviving demand from farmers. Good arable land now sells for more than £6,000 an acre across the country. Previously, such prices were commanded chiefly in East Anglia, whose peaty, silty soils ensure farmers get several harvests of vegetable crops, Knight Frank said.

"Farming is an optimism game and after a couple of good harvests and better prices for the past two years, there's a renewed confidence," said Andrew Shirley, the firm's head of rural land research. "There are more farmers in the market."

Shirley estimates there is one more buyer for every five who were looking to purchase farmland a year ago. Farmers and agricultural businesses make three in every five purchases now, he estimates.

Demand from "lifestyle" buyers has slowed and been overtaken by professional farmers, partly reflecting the impact of the difficulties in financial markets.

A separate index of country homes in the UK released earlier this month by Knight Frank showed the value of cottages, farmhouses and country manors declined 0.2 percent in the first quarter, a second quarterly drop.

Shirley said the pound's decline against the euro and other currencies has also attracted farmers from Ireland and Scandinavia, where land is more expensive and unlikely to rise higher.