SINCE the start of the year Yorkshire stone and slate to the value of more than £20,000 has been stolen in Wharfedale and Aireborough alone.

Patios have been dug up, garden walls dismantled and roofs stripped of stone.

Thieves dress to look like workmen and will even operate during the day - confident that people will believe they are legitimate contractors.

While Ilkley and Addingham have escaped the worst of these raids, the thieves have had a field day in the area from Otley to Horsforth. Since January, Weetwood Police has received 43 reports of theft from homes, businesses and historic buildings.

In Otley, the Dales Veterinary Centre, Bridge Street Surgery and Leeds City Council's One Stop Shop - all within a short distance of each other - had tiles stripped from their roofs in one night.

In Hawksworth, several homes had stone patios dug up during one weekend with one householder returning home at lunchtime to surprise thieves parked in a Transit van in his driveway.

Police, who believe the stone is being transported to builders in the South of the country, are urging everyone to be vigilant and to report sightings of people working on walls - even though they might appear quite innocent.

Peter Krushniak, neighbourhood watch liaison officer at Weetwood said thieves often put what look like legitimate builders stickers on the side of their vehicles, and have even used motorway maintenance stickers to pose as bona fide workers.

They have also stacked bags of cement near to the stones or slates they are stealing to make themselves look even less conspicuous.

He said: "There is very little we can do to stop these thieves. My advice isn't just to householders, it's to their neighbours.

"I urge people to write vehicle makes, colours and registration numbers down if they see vehicles at neighbours' houses, and call us.

"If it's a false alarm we don't mind, if we get a call while it's happening there is a good chance of catching these thieves."

Last month the 17th Century Puritan Chapel at Bramhope was hit by thieves who were surprised half way through stripping the roof of its tiles.

The theft, which came just after residents had been warned against a spate of the crime in the village newsletter, left the parish council with a hefty bill to cover the cost of putting the slates back.

It is hoped that new security measures will be put in place at the chapel in a bid to stop further attempted robberies.

Bramhope parish and Leeds city councillor Clive Fox said: "Yorkshire stone and slate are part of our local heritage, and quite apart of the cost, it's having an impact on the local environment.

"I understand a lot is stolen to order and is going out of the area, which is totally out of place.

"The message to people is eternal vigilance - people are going to have to be suspicious, they may be seen as busybodies, but we need to crack these crimes."

Sheila and Michael Robinson from Old Lane, Hawksworth, in the summer had their patio, worth around £2,000, stolen in the middle of the day.

Nobody was home at the time, but Mrs Robinson returned home and discovered that the patio had been stolen.

Mrs Robinson said: "You don't feel that you want to replace it in case it goes again, but we shouldn't have to make a sacrifice. You've got to be really nosey about what's going on, and that's not nice."

And Mr Robinson added "It's absolutely deplorable. We haven't replaced the patio yet, but we are going to increase security at our house. It's frightening that my wife could have returned home at any time to find three men and their van in the driveway."

Meanwhile, suppliers of stone have also suffered as a result of the increasingly common crime.

Wharfedale Reclaimed Stone, based at Gallows Hill, Pool Road, Otley, has experienced knock-on effects from the crimes.

Mark Philipson, who owns the company with business partner Andrew Mills, said: "If someone comes into our yard, we have to watch who we buy from.

"We can only buy from people we know, because we can't trust that people we don't know got the stone from legitimate places. "Because of this, the thieves may go to Bradford, and some yards might buy the stone meaning they are able to undercut us because of the way they got their goods."

Mr Philipson said he also thought the thieves followed vans from stone yards to the delivery point and then stole the stone from there.

He also thought that the crimes were on the increase and he often heard from individuals who had had stone stolen, and who were inquiring whether the firm has had anything.

"We get calls about once a week from people asking if we have had any stone in from people we don't know.

"We don't buy from people we don't already know, but the difficulty is that once the stones have been pinched, there is no way of identifying them."

Anyone with information on the thefts, or who have seen something suspicious is urged to contact Weetwood Police Station on 0113 2413459.