As newspapers rushed to follow up the News of the World exclusive late on Saturday night, Malcolm Rifkind, Secretary of State for Defence, defended Sir Peter, saying he had 'total confidence in the professional abilities of his Chief of the Defence Staff'.
Less than 24 hours later - a lot sooner than in the case of some ministers, but as soon as the extent of the News of the World material became known - he had no option but to quit over the relationship with Lady Buck, ex-wife of a former Navy minister.
Sir Peter, 60, had reached the pinnacle of his career through sheer hard work and single-minded devotion. He was named Chief of Defence Staff in May 1992. With it went the rank of Marshal of the RAF. In effect, this is the most sensitive and crucial post in the military hierarchy, a job which, it is said, requires the skills of a diplomat, a strategist and a warrior.
Sir Peter, an expert on relations with the Russians, took a number of key appointments as his career progressed, including one at Nato's Shape military headquarters. He was assistant chief of staff for plans and policy for the Supreme Allied Commander in Europe in the early 1980s, and Commander-in-Chief of United Kingdom Air Forces from 1985 to 1988, when he became Chief of the Air Staff.
A Londoner by birth, he joined the Royal Air Force in 1952. He is a pilot of prodigious experience having flown 128 types of aircraft, including the Russian Su-27 Flanker.
Menzies Campbell, the Liberal Democrat defence spokesman, said: 'To become Chief of Defence Staff, a man needs outstanding abilities. Sir Peter Harding had those in full measure, and so long as his ability to do his job was unaffected, I can see no reason why he should have resigned.'
But the single-minded career officer presided over the most traditional section of British life where marriage and family life are revered and adultery is an affront to accepted values. Sir Peter, an accomplished jazz pianist as well as a 'five-star' serviceman, and his wife Sheila have four children.
Labour demanded an inquiry to ensure that the affair had not given rise to any security lapses.
David Clark, the party's spokesman on defence, said: 'This man knew all our military secrets and one must be absolutely certain that there have been no lapses in our security.'