LONDON — The Royal Bank of Scotland said on Tuesday that John Maltby would step down as chief executive of Williams & Glyn, the unit it plans to spin off by the end of next year.

Mr. Maltby, the former head of commercial banking at the Lloyds Banking Group, will leave to serve as an adviser to a consortium of investors who participated in a 2013 bond offering to help finance the spinoff.

He will be succeeded by James Brown, the chief executive of R.B.S.’s Ulster Bank business.

“I would like to express our thanks to John Maltby for his very significant contribution to Williams & Glyn over the past 18 months,” Ross McEwan, the R.B.S. chief executive, said in a news release.

“Much has already been done in building a stand-alone business and we are grateful for the important role that John has played in getting the bank to this point.”