Hillman was born into a political family, related both to American labour leader Sidney Hillman and Chaim Herzog, sixth president of Israel. He was recruited to the Revolutionary Communist Party by Annie Roy in 1946 and joined its Kilburn branch. During this period he wrote to Natalia Sedova, Leon Trotsky's widow about questions relating to the Soviet Union and the history of the Left Opposition.
He became a critical member of the Socialist Review Group where he produced a document The Nature of the Stalinist Parties which was rejected by the group and replied to by Duncan Hallas This followed by a further document On Organic Unity where he advocated the group fuse with that of Ted Grant which led to his expulsion.
Hillman then joined Gerry Healy's Club however he became a secret sympathiser of the Revolutionary Socialist League. Hillman went on to become the RSL's treasurer and a founder member of the Militant editorial board. In 1961, whilst a member of the RSL, Hillman wrote a guide for members who were elected to councils: Notes on Council Work. In 1969, he volunteered to be and became President of the IFERS (International Flat Earth Research Society) which was created by the Dover based Samuel Shenton.
Hillman was elected in the 1958 London County Council election, representing Norwood, then in the 1961 election, he moved to represent Hackney Central. He kept his seat when it became the Greater London Council until 1981 where he chaired the Arts and Recreation Committee.
Hillman was elected to Barnet council in 1986 and when in 1994 it fell to a Lib-Lab alliance he was elected Mayor. His first act was to remove a bust of Margaret Thatcher from Barnet Town Hall.
He was the co-author in 1985, with journalist Richard Trench, of London Under London, one of the first books to describe in detail the variety of hidden rivers, tunnels, bunkers, crypts and cellars under Britain's capital city. He was also the founder and first president of the Lewis Carroll Society in 1969. He was also president of the international flat earth research society after Samuel Shenton.
- Richardson, A. "Ellis Hillman (1928-1996)" in Revolutionary History Vol. 6 no 2/3 pg.252
- Hillman, E. "Ellis Hillman and the Fourth International" in Revolutionary History Vol. 6 no 2/3 pg.188
- Hillman, E. "Ellis Hillman and the Fourth International" in Revolutionary History Vol. 6 no 2/3 pg.189-90
- Higgins, J. "Cliff Hanger: Ellis Hillman and the Socialist Review Group" in Revolutionary History Vol. 6 no 2/3 pg.254 Hallas' document 'The Stalinist Parties'
- Higgins, J. "Cliff Hanger: Ellis Hillman and the Socialist Review Group" in Revolutionary History Vol. 6 no 2/3 pg.254
- Birchall, I. Tony Cliff: A Marxist for His Time Bookmarks: London pg.143-44
- Crick, M. (1986) The March of Militant Faber and Faber: London pg.47
- Taaffe, P. (1995) The Rise of Militant Fortress: London pg.8
- Richardson, A. "Ellis Hillman (1928-1996)" in Revolutionary History Vol. 6 no 2/3 pg.252-3
- Harrington, I "Obituary: Ellis Hillman" Independent 24 January 1996
- Richardson, A. "Ellis Hillman (1928-1996)" in Revolutionary History Vol. 6 no 2/3 pg.253