He served in Italy as operations and intelligence officer to No 324 Squadron under Group Captain W. G. G. Duncan Smith (father of the future Conservative leader).

[3] One of Rees's Spitfire pilots in Italy, Frank Cooper, became his Permanent Secretary at the Northern Ireland Office.

One month after Rees's appointment, he lifted the proscription against the illegal loyalist paramilitary organisation, the Ulster Volunteer Force (UVF) to bring them into the democratic process.

Rees' decision to permit the Sunningdale power sharing arrangements to collapse in Northern Ireland was described as 'supine' by former SDLP leader, Seamus Mallon.

[10][11] In September 1976 Rees was appointed Home Secretary and remained in that post until Labour's defeat in the 1979 UK elections.

[12][13][14] Rees was president of the Video Standards Council from 1990 and was the first Chancellor of the University of Glamorgan, a position he held from 1994 to 2002.

In late 2005, a fall at his home in Southwark caused him to lapse into a coma, from which he never emerged; he died at St Thomas's Hospital on 5 January 2006, at the age of 85.