His formal resignation is expected soon, but he will remain in his position to oversee an orderly handover of his responsibilities.
Chairman Philip Hampton said:
“Nathan did a remarkable job as Chief Risk Officer and was integral to the plan which restored safety and soundness to the bank following the 2008 banking crisis. He leaves with the best wishes of the Board."
Chief Executive Ross McEwan added:
"I had the opportunity to work with Nathan through the autumn as we announced the new capital plan for the bank. He is a talented banker who brought a huge amount to our discussions with our regulators and our majority shareholder. While I'll miss working with Nathan, I look forward to competing with him in the UK market as we strive to better the industry for our customers."
Details on arrangements for his successor will be announced in due course.