The Barclay brothers, the secretive owners of the Telegraph Group, claimed that the value of their trophy property asset, London's Ritz Hotel, soared by a fifth last year to a record £600m, despite plummeting prices across the commercial real estate sector.

In recently filed accounts, for the year ended December 31 2007, Ellerman Investments, which owns the Ritz Hotel, The Ritz Club Casino and The Cavendish Hotel, said London's most famous hotel could be worth in more than £600m.