The letter announcing his retirement of Sir David Nicholson suggests he planned his departure more than a month-and-a-half ago.
Although it is dated May 21, one paragraph says: "In getting ourselves ready for the 1 April 2013 we should..." which implies that the letter was drafted before April 1 - the day that the controversial NHS reforms were implemented.
Sir David goes on to say that he has stayed in the role to oversee NHS reforms come into place.
He thanks NHS England's chair Professor Sir Malcolm Grant for support and understanding "with regard to the complexity of my role".
Professor Grant replied: "Thank you for your letter conveying your intention to retire as CEO of NHS England. I was sorry but not surprised to have it.
"Your career within the NHS over 35 years has been exceptional, and your leadership through the radical changes of the past two years has been fundamental to their success."
Commenting on the announcement by NHS boss Sir David Nicholson that he will retire next year, Chief executive of the NHS Confederation Mike Farrar said:
"Despite the difficulties of recent months, today's announcement provides an opportunity to focus on Sir David's contribution to the NHS over the past three decades, the significant achievements over the lifetime of his career and during his time as the chief executive of the NHS.
"Sir David came into office as NHS chief executive in 2006 and immediately led a major recovery from the deficit that the health service faced at that time.
"Over subsequent years he led the delivery of a remarkable reduction in waiting times for urgent and elective care, with access to treatment improving faster than almost any comparable health system.
"There have been significant improvements in patient outcomes and a huge reduction in healthcare acquired infections. In recent years, he presided over the largest structural reform in the history of the NHS."
Asked for David Cameron's response to Sir David Nicholson's retirement and assessment of his record, the Prime Minister's official spokesman said: "He agrees with the Secretary of State for Health."
Mr Cameron's view of Sir David was "unchanged" since the PM responded to the Francis report on Mid-Staffordshire, said the spokesman.
He said he was not aware of ministers discussing the NHS chief's departure with Sir David in advance, adding: "It is his decision to retire."
Julie Bailey, from the campaign group Cure The NHS, has led the calls for Sir David Nicholson to resign.
Ms Bailey, who set up the group after her mother Bella died at Stafford Hospital in 2007, said that since the Mid Staffordshire public inquiry report was published, Sir David's position had been "untenable", adding: "It is fantastic news.
"This is the start of the cure for the NHS.
"We can start to look to the future now. He was part of the problem - not part of the solution.
"We now need a leader who will galvanise and inspire the front line, not bully them."
Sir David Nicholson has written a letter outlining his intention to retire in March next year to the chair of NHS England Professor Malcolm Grant. In it he writes:
Whilst I believe we have made significant progress together under my leadership, recent events continue to show that on occasion the NHS can still sometimes fail patients, their families and carers. This continues to be a matter of profound regret to me but please know that on a daily basis I continue, and will always continue, to be inspired and moved by the passion that those who work in the NHS continue to show.
This video was filmed by ITV News correspondent Rupert Evelyn:
NHS boss Sir David Nicholson plans to retire in March next year, NHS England said today.
Peter Carter failed to reply to ITV News Correspondent Rupert Evelyn's question despite being asked several times for a clear answer:
NHS chief Sir David Nicholson has said he is "absolutely completely committed" to the NHS despite questions about his future. He has been criticised for his role in the Mid Staffs hospital deaths scandal.
Health experts have asked Sir David Nicholson to delay the launch of the new telephone triage system NHS 111, as they say the crisis affecting the system will put patient safety at risk.
The phone number, designed to direct people with non threatening conditions to the right part of the NHS, will be launched nationwide on Monday.
But the British Medical Association said problems had occurred during the trialling of the number.
They added that in some areas, switchboards could not cope with the volume of calls, which had also been affected by severe IT failures.
In a statement, the NHS said: "We are confident that measures now in place will ensure resolution of these early problems."