Fresh doubt was today cast on the valuation of the Gem of Tanzania, the ruby valued at £11 million in the accounts of collapsed Shifnal builder Wrekin Construction.

The London expert said to have signed the valuation certificate says it is a forgery.

He said: “It’s a damn good copy but it’s not my signature on that document.”

David Davis said a valuation he did carry out for the stone’s original owner several years ago, might have been for £11 million at the exchange rate of the time.

But he said that would have been a replacement value for insurance purposes. More than 400 people lost their jobs when administrators were called in this month.

Solicitor, Derek Miller said Wrekin’s owner Tamar Group believed the stone could be worth £11m.