Carphone Warehouse co-founder David Ross today ploughed £250,000 into Big Yellow, the self-storage firm where he quit as a director last year, as the City prepared for a fresh wave of fundraisings.

Big Yellow hopes to raise about £25 million by selling 11.6 million new shares to fund the construction of six sites in London and one in Guildford.

Ross, who holds a 9.92% stake in the firm, pledged to increase his holding along with current members of the board including chairman Nick Vetch. Together, they will buy £680,000 worth of shares with Ross investing £250,000.

The stock rose 5p to 276p today to value Big Yellow at £323 million.

Vetch said business remained "unquestionably difficult" but things had improved in the last two months.

Ross was forced to resign from the boards of Big Yellow, Carphone and National Express last year after he pledged some of his shares in the companies as collateral against loans.

He also quit as Boris Johnson's finance adviser for the 2012 Olympics.

Ross still holds a 19.4% stake in Carphone which he set up with Charles Dunstone in 1989.

London-based property companies Great Portland Estates and Shaftesbury also said they were considering how to raise new funds to take advantage of bargains in the recession. Analysts reckon both firms could look to raise as much as £150 million each.