166 (Mixed) Heavy Anti-Aircraft Regiment RA (TA) was formed at Lipson, Plymouth in August 1942 with two batteries. The Regiment served with Anti-Aircraft Command for its entire existence. 166 (Mixed) Heavy Anti-Aircraft Regiment RA (TA) was disbanded in May 1945 at Milford Haven, Pembrokeshire.
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.
| Aug 42 | Formed | Plymouth, Devon, UK | |
| Aug 42 |  |
8 Anti-Aircraft Division, 55 Anti-Aircraft Brigade | Plymouth, Devon, UK |
| Aug 43 |  |
3 Anti-Aircraft Group, 45 Anti-Aircraft Brigade | South West, UK |
| Aug 44 | |
3 Anti-Aircraft Group, 61 Anti-Aircraft Brigade | South Wales, UK |
| May 45 | Disbanded | Pembrokeshire, UK |
Batteries
| Aug 42 | 549 (Mixed), 555 (Mixed) |
| May 43 | 549 (M), 555 (M), 580 (M) |
| Mar 45 | 549 (M), 555 (M) |