THIEVES who spent hours stealing thousands of pounds worth of lead from the grounds of a famous museum are thought to have been mistaken for workmen.

They stripped 30 metres of lead flashing, up to 12ins wide, from two lodge houses at the gates of the Bowes Museum in Barnard Castle, County Durham.

Gaps where the lead should have been were noticed by one of the staff on Tuesday morning, but it could have been taken at any time during the previous four days.

Police are hoping to hear from anyone who saw men working on the two roofs at any time after lunchtime last Friday.

Sergeant Brendan Coll said yesterday: "It takes a long time to chisel out this amount of lead. It is certainly not something you can do in ten minutes.

"I think the thieves must have been mistaken for official workmen. The lodges are right beside a busy road, so I would be astonished if nobody saw them during the time they were busy on the two roofs.

"Anyone suspicious of them would probably have called the police right away. But nobody would give them a second thought if they looked and acted like genuine workers."

The lodges, both listed buildings put up when the museum was built over a century ago, are used mainly for storage, but none of the priceless exhibits are ever kept in them.

A museum spokesman said it was not known if the lead was taken during the day or night, but it was expected to cost up to £4,000 to replace it.

Ruth Robson, head of marketing and development at the museum, said: "The maintenance of this beautiful Grade I listed site already has its challenges, and we could do without problems like this."

Sgt Coll appealed to anyone who saw men busy on or near the lodges to call police on 0845 6060365.