| Dates | Locations | Batteries | Remarks |
| | | |
| 1947.04.01 | RHQ 2nd Heavy Anti-Aircraft Regiment RA re-titled 21st Heavy | | |
| Anti-Aircraft Regiment RA, with 20, 57 and 71 HAA Btys redesignated | | |
| from 15 Coast Bty (personnel from 28 HAA Bty), 16 and 20 HAA Btys, | | |
| | respectively. | | |
| 1947.04 | Wales: Kinmel Park Bks, Rhyl | 20, 57 and 71 HAA Btys | 3.7" Gun |
| Late 1947 | England: Wrottesley Park, near Wolverhampton | 20, 57 and 71 HAA Btys | 3.7" Gun |
| 16 Oct 48: Reduced to cadre and RHQ, 20, 57 and 71 Btys concurrently | | |
| reformed from personnel of RHQ 88th HAA Regt and 253, 254 and 258 HAA | | |
| | Btys respectively. | | |
| 1948.10 | England: Harrington Bks, Liverpool | 20, 57 and 71 HAA Btys | 3.7" Gun |
| 1951 | England: Saighton Camp, Chester | 20, 57 and 71 HAA Btys | 3.7" Gun |
| 1952 | England: Lindsey Street Trg Depot, Newcastle | 20, 57 and 71 HAA Btys | 3.7" Gun |
| ? | England: ? Bks, Woolwich | 20, 57 and 71 HAA Btys | 3.7" Gun |
| c1953? | England: Saighton Camp, Chester | 20, 57 and 71 HAA Btys | |
| | 1 May 55: RHQ and Btys reduced to cadre at Chester. | | |
| 15 July reformed at Redford Infantry Bks, Edinburgh as 21st Medium | | |
| Regiment (20, 57 and 71 Btys) from personnel of 60th Medium Regt RA | | |
| | (100, 224 and 228 Btys respectively), equipped with 5.5" gun. | | |
| 1955.08 | Scotland: Redford Bks, Edinburgh | 20, 57 and 71 Med Btys | 5.5” Gun |
| Jul 56 – Jul 57: Cyprus: Stroumbi & Eastend Camps, Paphos district | | Infantry role |
| 17 Feb 58: 71 Bty placed in suspended animation (disbanded 1/1/62) and | | |
| | 7 Bty joined the Regt ex 15th Med Regt RA. | 7, 20 and 57 Med Btys | |
| 1959 | England: Bradbury Lines, Hereford | 7, 20 and 57 Med Btys | 5.5” Gun |
| 1960.12 | Wales: Kimnel Park Camp, Rhyl | 7, 20 and 57 Med Btys | 5.5” Gun |
| 31 Oct 61: 20 Bty placed in suspended animation (later in 95 Cdo Regt RA). | | |
| | 30 Nov 61: 7 Bty placed in suspended animation (later in 95 Cdo Regt RA). | | |
| 1962.01 | Germany: St Barbara Bks, Fallingbostel | 57 Bty | |
| Jan 62: 14 Bty joined the Regt ex 94 Regt RA. | 14 and 57 Loc Btys | |
| Renamed 21st Locating Regiment Royal Artillery: 14 Bty equipped for | | |
| Meteorology and Survey, 57 Bty equipped with Drone and Robert systems. | | Meteorology & Survey: Drone & Robert |
| 29 Apr 64: 57 Bty moved to 94 Regt. | | |
| 15 Jun 64: RHQ & 14 Bty placed into suspended animation. (14 Bty later | | |
| in 16th Lt AD Regt RA). | | |
| 15 Jun 1964 – Suspended Animation | | |
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