A Singapore sovereign wealth fund has placed an order for shares in Britain's Royal Mail ahead of its privatization, a report said late Sunday. The Government Investment Corporation is set to become a "significant" shareholder in the postal service, Britain's (Sky News) said. It did not say how many shares it had ordered ahead of the initial public offering, which is estimated at up to 3.3 billion pounds (5.3 billion dollars). Britain's Conservative-Liberal Democrat coalition is selling up to 70% of the state-owned Royal Mail, which dates back to 1516. Trading is expected to start in the middle of October. Postal workers have threatened to strike in protest.