20 Anti-Tank Regiment RA was formed in November 1938 by conversion of 20 Field Brigade RA with four batteries. It served the entire war with 3 Infantry Division. After fighting with the BEF in France in 1940 it than trained at home until D-Day in 1944. In April 1947 20 Anti-Tank Regiment RA was converted to 57 Heavy Anti-Aircraft Regiment RA.
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.
| 3 Sep 39 |  |
5 Infantry Division Attached 3 Infantry Division |
Catterick, Yorkshire, UK |
| Sep 39 |  |
3 Infantry Division | France |
| Jun 40 |  |
3 Infantry Division | Lockerbie, Dumfries, UK |
| 6 Jun 44 | |
3 Infantry Division | Normandy, France |
| 1944 | |
3 Infantry Division | Kervenheim, Germany |
| Feb 45 | |
3 Infantry Division | The Rhine, Germany |
Batteries
| Nov 38 | 41, 45, 67, 99 |
| Jul 41 | 41, 45, 67, 99, 101 |
| Sep 41 | 41, 67, 99, 101 |
| Jun 42 | 41, 67, 101 |
| Jun 43 | 41, 45, 67, 101 |
Equipment
| 1939 | Light Dragon Mk 2 |
| 1944 | M10 3 inch Self Propelled |
| Jun 44 | 41 Battery – B Troop 4 x M10, A & C Troops each 4 x 6 pdr (Lloyd tractors ?) |
| Jan 45 | Change over to Archers began |
| 1 Feb 45 | 9 x 17pdr Self Propelled Archer, 36 x 6 pdr, 4 x M10 3 inch Self Propelled, 3 x Crusader AA (Polsten) “Chargers” |
| Mar 45 | 18 x 17pdr towed, 18 x 17pdr Self Propelled Archer, 7 x 75mm & 4 x 6 pdr Valentine “Chargers” |
“Chargers” were gun armed tanks for officers as battlefield transport. OP tanks had a dummy gun and were used for observation and fire control.