The full statement sent out at just after 10am today (Monday 4 September) reads:
"I have today resigned as CEO of Bell Pottinger.
"In June I commissioned Herbert Smith to look at the details of the work we undertook for Oakbay, the findings of which will be published shortly.
"Having read these findings, I recognise the business requires a change of leadership to fix the problems of the past and to move forward.
"Although I neither initiated nor was involved in the Oakbay work, I accept that as CEO, I have ultimate executive responsibility for Bell Pottinger.
"I feel deeply let down by the colleagues who misled me. However, I think it is important I take proper accountability for what has happened.
"I have also striven to put the best interests of Bell Pottinger and its brilliant staff first, and it is for that reason that I am stepping down today.
"I would like to thank all of the Bell Pottinger staff and clients who have supported, and continue to support me. The business will now move forward in the best interests of its clients and staff."
Henderson's statement was accompanied by a comment from chair Mark Smith.
He said: "James has always had the best interests of the business at heart, especially during the recent, difficult months. He was not involved in the Oakbay account but as CEO he believes he must take ultimately responsibility. That is a laudable decision."