The bank, which is majority-owned by the UK government, said the referendum result was a surprise for many, but reassured it had planned “extensively” for both possible outcomes.

Royal Bank of Scotland's chief executive, Ross McEwan, has written to staff alerting them of the “range of unknowns” the Brexit vote has created for the UK's short-, medium- and long-term economic prospects.

In an internal memo sent on Tuesday, he highlighted significant falls in the value of the British pound, the value of many British companies and the value of UK and European banking stocks – including that of RBS. Indeed, trading in RBS was briefly halted on Monday thanks to the London Stock Exchange's automatic circuit breakers when shares in the bank plunged 15 per cent from their opening price.

“Despite the noisy fallout from the vote, many of the fundamentals remain true. Our view as a bank is that the UK remains a large, well developed economy with good long-term prospects. It's our home market and our job as a leading bank here is to help it succeed," McEwan said.

“Last week before the vote, we had 16 million customers that needed serving well. Today we have the same number and our job remains the same – to look after their needs better than anyone else.”

He commended colleagues on the trading floors, across the frontline and in finance, communications and supporting roles, who “did us all proud” in the immediate afermath of the vote.

New Zealand-born McEwan stressed that the diversity of RBS staff remains key to the bank's success.

“As someone born outside the UK, I see one of this country's biggest strengths as its openness to the rest of the world, and the people of it. As a major employer and backer of the economy we have a duty to ensure that we reflect that.”