Operating costs rose to £232 million from £225 million over the period. However, when strategic, litigation and conduct costs are stripped out, operating costs fell by £3 million, RBS said in a statement today.

Assets under management in private banking remained broadly stable. For the year to date, growth of £2.1 billion reflects positive investment performance of £1.9 billion following adverse market movements in late 2018 and net new business of £200 million, RBS said. Total assets under administration and management in private banking rose by £400 million to £28.9 billion versus the end of June last year.

"What has been particularly pleasing has been the 13% increase, on last year, in new clients that we have welcomed to Coutts and Adam & Company. This naturally augurs well for the longer term health of our business, as these client relationships grow over time," Peter Flavel, chief executive of Coutts, said.

“We’ve continued to make good and strong progress in the first half of 2019 . We’ve increased AuMs by 10 per cent and our investment performance has been equally strong. Return on equity, a key measure for us, has now increased to 16.6 per cent," he added.

For RBS as a whole, the banking group – which remains part-owned by the UK government after the post-crisis bailout of late 2008 – reported an operating profit before tax of £2.694 billion, an attributable profit of £2.038 billion and a return on tangible equity of 12.1 per cent in the first six months of 2019.