Thieves have stolen a valuable exhibit from one of Brighton's historic buildings.

The walk-in thieves unscrewed an 18th Century musical bracket clock from a mantlepiece at Preston Manor in Preston Drove.

David Beevers, keeper of the manor, said he suspected the clock, which is 58cm high and is worth £10,000, was stolen to order.

He said: "The clock is the most popular item in the manor. It plays every hour and has ships going across above the face. The children just love it.

"This is extremely upsetting and I just pray we get it back."

Last May burglars escaped with £70,000 of antique silverware from Preston Manor.

Yesterday's theft took place at about 4.15pm as the two thieves were walking round the manor.

One pretended to have left keys on a table and while staff were distracted his accomplice grabbed the clock from the Morning Room and ran out.

Staff pressed panic buttons and police were at the scene in minutes but the offenders escaped.

The thieves were both 20 to 25 and over 6ft tall. One wore a baseball sweatshirt with the words Nike Athletic across the chest. The other had curly black hair and wore a dark rain coat.

Witnesses or anyone with information should contact Brighton police on 0845 6070999.