[2] On 18 December 1943, having reached the rank of leading aircraftman, he was granted an emergency commission as a pilot officer on probation in the RAFVR.

[2] In July 1945, he was shot down over Phuket Island by the Japanese: after an emergency landing offshore, the injured Gregory swam out to sea while under heavy fire, before being rescued by a Walrus flying boat.

[1] This amalgamation created tensions and split loyalties throughout the force in the early years, and were cited as a major cause of issue relating to the hunt for the 'Yorkshire Ripper'.

[2] Gregory directly contributed to the delay in finding Sutcliffe through his support of the 'Wearside Jack' cassette tape and letters; these were later revealed to be a hoax but diverted detectives for two years into chasing a non-existent lead.

[1] That line of inquiry produced "100 per cent rubbish",[2] and, in July 1979, Sutcliffe was interviewed for the fifth time but was dismissed as a suspect because his voice and handwriting did not fit 'Wearside Jack'.

[10] He was finally arrested on 2 January 1981 by a neighbouring force for a traffic offence, although further investigation of the scene the following day revealed a hammer and knife: the 'Yorkshire Ripper' had been found and Sutcliffe readily confessed to 13 murders.

[2][10] Gregory swiftly called a triumphant press conference, stating that he was "delighted with developments at this stage" and announcing the immediate scaling-down of the Ripper manhunt.

[2][8] The later inquiry into the manhunt's failings was highly critical of Gregory's decision to appoint George Oldfield as senior investigating officer: he only undertook the role part-time in addition to his duties as assistant chief constable (crime), and he was not considered to have had the professional competence and charisma to effectively lead such a large inquiry.

[1][8] One survivor of an attack by Sutcliffe was only awarded £17,000 in compensation after a long legal fight,[12] and as chief constable he had banned his officers from speaking to the press.

[3] In the 1971 New Year Honours, Gregory was awarded the Queen's Police Medal for Distinguished Service (QPM) in recognition of his work as chief constable of West Yorkshire Constabulary.

[14] In the 1980 Queen's Birthday Honours, he was appointed Commander of the Order of the British Empire (CBE) in recognition of his work as chief constable of West Yorkshire Metropolitan Police.