Royal Bank of Scotland Group, Britain’s biggest government-owned bank, agreed to sell 318 branches to Spain’s Banco Santander, a disposal forced on the lender following its taxpayer-funded bailout. Santander will pay £350ms ($558m) more than the branches’ net asset value when the purchase is completed by December 2011, the Edinburgh-based lender said in a statement today. That values the branches at about £1.7bn ($2.7bn).