By Rupert Hargreaves Natwest has bought back another chunk of shares from its largest shareholder, HM Treasury. This morning, the company announced that it had purchased 392m shares from the government, representing 4.5 per cent of its share capital. The lender paid 316.2p per share for the stake, spending a total of £1.24bn to acquire the shares from the government. In addition to this announcement, this morning, it was revealed that the government had also reduced its stake further under its regular trading plan. Following the deals, the government’s stake in the lender has fallen to 22.5 pe…