Nicholson was born in Nottingham in 1956 and educated at Forest Fields Grammar School. He graduated from Bristol Polytechnic with a history and politics degree and began work in the health sphere. At the same time as starting work in a mental health unit after university he joined the Communist Party in 1977.
By 1980, he was a member of the Huddersfield branches of both the Communist Party and YCL, having previously been active in the local Anti-Apartheid movement. He was most certainly an opponent of the leadership on issues such as Poland and Afghanistan and described himself as having being a "tankie" in an interview in "The Guardian" shortly after he was appointed Chief Executive of the NHS.
He does not however seem to have been associated with "Straight Left", by the account of a contemporary who holidayed with him. SL was, at that time the only organised opposition faction in the Yorkshire district of the Party (this being before the split over the Morning Star that led to the CPB). Despite his views on foreign policy, Nicholson seemed to have agreed with the growing revisionist tendency in the Party on some issues to the extent of being able to get on the recommended list at the Yorkshire District Congress in 1983, when other oppositionists were excluded by what was, even as early as this, a particularly virulent local revisionist tendency.
In the Guardian interview, he said he drifted away, implying that he probably did not resign over any political point but just didn't re-card; this would probably be the 1985 card issue. One former member of the Straight Left faction definitely remembers him attending a secret week-long SL summer school in North Wales in 1984. This implies that he had finally linked up to SL only months before leaving the Party. (NB Nicholson seems to have hinted to the media that 1983 was the date of his departure from the Party, which differs from at least two contemporary witnesses by at least two years.)
The intensely divisive atmosphere in the Party during 1984 – the year of the miners’ strike and this was Yorkshire – may have helped along his dropping out of collective political discussions after that summer. In turn, this may have cut him adrift, aided with his now beginning to earn an increasingly large salary, which also denied him the right to take part in political activities.
For the next two decades he climbed the career ladder in the NHS, being appointed Chief Executive of Birmingham and The Black Country Strategic Health Authority in 2003. The London Strategic Health Authority followed and in 2006 the role of NHS Chief Executive. Sir David was chief executive of the body overseeing the Mid Staffs NHS Trust for a period when death rates were found to be high.