Oxfordshire's black market scrap metal trade has been struck by the global recession.

The illegal trade soared for two years, as the price of scrap more than doubled, leading thieves to steal lead from church roofs, grab metal bins from the streets and tow away old cars.

But as the demand for scrap falls, police have noticed a sudden reduction in thefts over the past three months.

Insp Sean Hodgson, head of Thames Valley Police’s crime prevention section, has launched Operation Precious, signing up scrap metal dealers to try to end the illegal trade.

The price of scrap metal has halved in the past six months, with the price of a tonne of copper falling to £1,200 and aluminium down to about £300 a tonne, according to Robert Bradford, of Oxford firm Metal Salvage.

A scrap car would have earned up to £140 last summer but is now worth just £50.

Mr Hodgson said: “Metal theft went crazy last year but we’re seeing it calming down.

“There’s a drop in the world economy and demand for scrap metal, so there’s a lull in metal theft as a result.

“We’re trying to take advantage of this and work with the scrap metal dealers so that we have everything in place if it picks up again.

“We want to work with the scrap trade and reduce the opportunities for people to dispose of metal.”

Between April 2007 and March last year there were 788 metal thefts in Oxfordshire.

Since last April, 730 incidents have been reported but Mr Hodgson said almost all these thefts happened before September, around the time prices began to fall sharply.

About 20 of Oxfordshire’s scrap dealers have signed up to Operation Precious so far.

Dealers have changed their records to include more details of where metal comes from and is sold on to. Anyone wanting to sell scrap metal at their yards must provide photo identification and a utility bill.

Police will also carry out regular visits and licence inspections.

Metal Salvage, in Jackdaw Lane, in East Oxford, has signed up to the charter.

Mr Bradford said: “Theft has gone down because the price has fallen. There’s been no money in it over the past six months so people haven’t been stealing it. We’ve definitely had less break-ins.”

In September, thieves stole £3,000 worth of lead flashing from the roof of Jaffe & Neale Bookshop and Cafe, in Chipping Norton, days after metal stolen previously had been replaced.