A valuation certificate for 'The Gem of Tanzania', a huge ruby supporting the creditworthiness of failed civil engineer Wrekin Construction, was forged, according to its purported signatory.

The news further weakens claims in the 2007 accounts of Wrekin that the gem had a market value of £11m, on which the confidence of suppliers, customers and lenders was partly based.

The ruby, which weighs more than 2kg, was valued in 2004 by David Davis, a London-based gem setter and expert on rare uncut stones.

A certificate apparently signed by him and stating a market value of $22m-$23m is among the supporting documents held by David Unwin, purchaser of the ruby and owner of Wrekin.

However, when the FT showed Davis a copy of the word-processed certificate, which included a photograph of the ruby, he said it was a forgery.

Financial Times