Traditional banking-related activities, as defined by interest income, still account for over 60 percent of the total income of Coutts and Company, the biggest element of Royal Bank of Scotland’s (RBS) private banking interests.

But according to the bank’s latest set of accounts, which have just been deposited at Companies House, non-interest income and especially investment management fees are growing much faster in both absolute and relative terms.

Net interest income amounted to £433 million or 63.58 percent of total income of £681 million for the year to 31 December 2018. This was a £47 million or 12.18 perce...