Formed in February 1920 as 1 London Brigade Royal Field Artillery (TF). It became 90 (1st London) Brigade RFA (TA) in 1921. It re-titled again in June 1924 as 90 (1st London) Field Brigade RA (TA). In April 1929 it became 90 (City of London) Field Brigade RA (TA). 90 Field Brigade was re-designated 90 (City of London) Field Regiment RA (TA) in November 1938 with two batteries. In January 1941 a third battery was formed. Post war 90 (City of London) Field Regiment RA (TA) went into suspended animation in May 1946 and was re-constituted as 290 (City of London) Field Regiment RA (TA) in January 1947.
Illustrations of the formation badges under which a unit served or supported are given. This is no guarantee that the unit used this formations badge.
| 1 Sep 39 | Regiment embodied | London, UK | |
| 3 Sep 39 |  |
London District | London, UK |
| Oct 39 |  |
56 (1 London) Infantry Division | Sussex, UK |
| Nov 39 | Cadre for formation of 56 (Newfoundland) Heavy Regiment | ||
| Nov 40 | |
56 Infantry Division | Kent coast, UK |
| 10 May 40 | |
56 Infantry Division Party provided to man AA/LMG on small craft for Dunkirk evacuation |
Suffolk, UK |
| Nov 42 | |
56 Infantry Division | Iraq |
| Apr 43 |  |
50 Infantry Division | N Africa |
| Jul 43 | |
50 Infantry Division | Sicily |
| Nov 43 | |
50 Infantry Division | UK |
| Jun 44 | |
50 Infantry Division | Normandy, France |
| Nov 44 |  |
2 Army | NW Europe |
Batteries
| 1921 | 357, 358, 359, 360 |
| Nov 38 | 357 (1st City of London), 358 (2nd City of London) – 359 & 360 Batteries to 138 Field Regiment |
| 1 Apr 41 | 357, 358, 465 |
Equipment
| Oct 39 | 4 x 4.5 inch Howitzers |
| 10 May 40 | 4 x 18 pdr, 4 x 18/25 pdr |
| Jun 44 | 25 pdr Self Propelled Sexton – Sherman V Observation Post tanks |