[1] He had an extremely long association with the Freedom newspaper in London, to which he regularly submitted his Wildcat comic strips.
In 1963 he played a key role in exposing Harold Challenor, a corrupt police officer who had unsuccessfully tried to frame him for carrying an offensive weapon, see below.
A resettlement grant following his discharge allowed him to study commercial design at Bradford Regional Art School from 1949 to 1953.
Rooum said that he first became interested in anarchism in 1944 when he visited Speaker's Corner in London while on a Ministry of Food scheme which used schoolboys to pick hops in Kent.
"[8] In 1963 Rooum exposed police corruption during demonstrations against the Greek State Visit in July by King Paul of Greece and Queen Frederika.
Some of the sentences were overturned on appeal and the Home Secretary, Henry Brooke, was required to offer financial compensation.
He held up a banner reading, "Lambrakis RIP", referring to a Greek MP and peace activist who had been murdered.
"[10] At the police station, the officer, Detective Sergeant Harold Challenor, "took from his pocket a screwed-up newspaper, which he opened with a flourish.
'"[10] Rooum was a member of the National Council of Civil Liberties and he had, by good fortune, read some material on forensic science and so gave his clothes to his defence solicitor Stanley Clinton Davis for analysis.
A subsequent enquiry found that he had probably begun developing paranoid schizophrenia for some months before the incident, but the lack of any successful prosecution against him was seen by some as evidence of further establishment corruption.
[15] In 1952, Philip Sansom invited Rooum to draw a regular cartoon strip for The Syndicalist and he contributed Scissor Bill.
Another exhibition, 'Emotional need', which featured Wildcat, the short film by Adam Louis-Jacob about Rooum's black and white strip cartoons for Freedom, was held at Collective in Edinburgh in 2017.