LONDON (MarketWatch) -- Shares of Royal Mail PLC UK:RMG 0.00% traded at 4.46 pounds ($7.13) on its first trading day, up 35% from the pre-float purchase price of £3.30 a share. The rally boosted the value of the previously state-owned company to more than £4.5 billion, compared with the £3.3 billion initial-public-offering price. U.K. Business Secretary Vince Cable said there had been 700,000 individual retail applications for the shares, with demand from private investors for the flotation seven times over-subscribed, according to media reports. The first two days of trading will be limited to institutional investors, and full trading will begin on Tuesday, Oct. 15 -- the day before the result of a strike ballot by postal workers. "The jump in the shares above 400p will certainly see the U.K. government being criticized for selling the company too cheaply, ripping off U.K. taxpayers," said Joe Rundle, head of trading at ETX Capital. "But it must be noted that institutional allocations (bid above £10k) have been scaled back this time, allowing allocation to retail clients which should go down neatly in general sentiment across the public," he added.