The burglars broke into Cromford Mill snatching the face and mechanism of the clock which is estimated to be worth £5,000.

But the thieves left behind the casing and dropped the its pendulum as they ran off at about 0630 GMT on 4 February, leaving their haul almost worthless.

The owners, the Arkwright Society, have appealed to antique dealers and market traders to look out for the stolen clock.

Plant motif

The Arkwright Society is an educational charity involved in the restoration of Sir Richard Arkwright's Cromford Mill, the world's first successful water powered cotton mill.

Sarah MacLeod, from the society, said the clock dates back to 1770 and is thought to have been made by one of Arkwright's employees.

"A vague estimate of its value is about £5,000 but in terms of its historical value it is the only one we have got.

"It is very important to the site - on the whole I shouldn't think we would find another one."

The clock has a distinctive face marked with the words "J Jeffryes Cromford" and carries a small bird and plant motif.