The bank formerly known as the Royal Bank of Scotland would be "too big" for the Scottish economy if the country were to become independent from the rest of the UK, its top boss has said.
And that would prompt a move of its headquarters to the UK, despite the vote for Brexit.
Read more: Goodbye, Royal Bank of Scotland
The bank worked up contingency plans in the event that Scotland voted to leave the UK in the independence referendum in 2014. It would have moved its headquarters south of the border.
Asked if the bank's position remained the same, McEwan said: "We'd have to make the same moves I suspect because the Royal Bank of Scotland, being domiciled in Scotland, would just be too big for the economy, even in the shape that we're building."
He said the move would not affect the 12,000 RBS jobs based in Scotland, however.
"Two years ago when we had the Scottish referendum, I made it very clear we'd have the people in the right place, that moving the plaque didn't make any difference to them," said McEwan.
There has been some indication from Scotland's First Minister Nicola Sturgeon that there may be a second vote on independence following the EU referendum.
In Scotland, the majority of voters supported remaining a part of Europe.
"If we can not protect our interests within a UK that is going to be changing fundamentally, then that right of Scotland to consider the option of independence always has to be there," said Sturgeon in the week's following the vote for Brexit.
McEwan also revealed the bank would soon make a name change, ditching the RBS name to escape its scandal ridden reputation of the past decade.