Santander is interested in the former Williams & Glyn's branch network, which disappeared as a brand off high streets in 1985 but was maintained as a legal entity.
The RBS branches are being sold under the orders of the European Commission to recover the billions of pounds in state aid the bank received. RBS' sale memorandum was sent out last week. However, it is understood that any buyer would have to find an extra £3bn apart from the mooted price of £1bn.
Santander became a household name in the UK when it acquired Abbey for £9.5bn in 2004. It reported a 13 per cent rise in fourth-quarter net profit to 2.2bn euros (£1.9bn), and is seen as the most successful retail bank in the Britain.
Doubts have grown in recent weeks about the willingness of National Australia Bank, another interested party, to clinch a deal with RBS. However, Virgin Money has made it clear it is still in the fray for the RBS' branches.
