The Regiment was formed in November 1943 by the re-designation of RHQ 18 Defence Regiment as RHQ L Medium Regiment RA. In January 1944 it embarked for North Africa and was re-designated 18 Medium Regiment RA. It was joined by its two Batteries. The Regiment disbanded in February 1945, 254 Battery going to suspended animation.
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.
| Nov 43 | Formed from HQ 18 Defence Regiment RA as RHQ L Medium Regiment |
UK | |
| Nov 43 | Home Forces | UK | |
| Jan 44 | Re-designated RHQ 18 Medium Regiment | ||
| Mar 44 |  |
GHQ Troops Middle East Forces | N Africa |
| Feb 45 | Disbanded |
Batteries
| Mar 44 | 254, 255 |