27 Anti-Aircraft Brigade was formed as 3 London Air Defence Brigade in 1922. It gained the title “Home Counties” 1935. The Brigade served in the South of England until being converted into an Infantry Brigade in January 1945. 27 Anti-Aircraft Brigade became 303 Infantry Brigade.
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.
| 1922 | Formed as 3 London Air Defence Brigade | | |
| 1935 | Became 27 (Home Counties) Anti-Aircraft Group |  | 1 Anti-Aircraft Division |
| Sep 39 | Lingfield, Surrey – Searchlight Brigade |  | 6 Anti-Aircraft Division |
| Feb 41 | Portsmouth, Hampshire |  | 5 Anti-Aircraft Division |
| Aug 42 | South East England |  | 3 Anti-Aircraft Division |
| Oct 42 | South East England |  | 2 Anti-Aircraft Group |
| Jan 45 | Converted to 303 Infantry Brigade |  | |
Order of Battle 1927
| 53 (City of London) Anti-Aircraft Brigade RA (TA) (157, 158, 159 Batteries) |
| 54 (City of London) Anti-Aircraft Brigade RA (TA) (160, 161, 162 Batteries) |
| 27 (London) Anti-Aircraft Battalion (London Electrical Engineers) RE (TA) (304, 305, 306, 390 Companies) – Searchlights |
| 27 (London) Anti-Aircraft Signal Company Royal Signals |
Order of Battle 1935
| 60 (City of London) Anti-Aircraft Brigade RA (TA) (168, 169, 194 Batteries) |
| 30 (Surrey) Anti-Aircraft Battalion RE (TA) (315, 316, 318, 323 Companies) – Searchlights |
| 31 (City of London Rifles) Anti-Aircraft Battalion RE (TA) (324, 325, 326, 327 Companies) – Searchlights |
| 34 (Queen’s Own Royal West Kent) Anti-Aircraft Battalion RE (TA) (320, 336, 337, 338 Companies) – Searchlights |
| 35 (First Surrey Rifles) Anti-Aircraft Battalion RE (TA) (340, 341, 342, 343 Companies) – Searchlights |
Order of Battle 1939
| 31 (City of London Rifles) Anti-Aircraft Battalion RE (TA) (324, 325, 326, 327 Companies) |
| 34 (Queen’s Own Royal West Kent) Anti-Aircraft Battalion RE (TA) (320, 336, 337, 338 Companies) |
| 70 (Sussex) Searchlight Regiment RA (TA) (459, 460, 461 Batteries) |
During August 1940 the RE Anti-Aircraft Battalions became Searchlight Regiments RA
Order of Battle November 1940
| 31 (City of London Rifles) Searchlight Regiment RA (TA) |
| 70 (Sussex) Searchlight Regiment RA (TA) |
Order of Battle December 1942
| 125 Light Anti-Aircraft Regiment (417, 418, 419 Batteries) |
| 1 Searchlight Regiment (1, 2, 7 Batteries – 8 Battery attached 71 AA Brigade) |
| 34 Searchlight Regiment (302, 337, 338 Batteries – 336 Battery attached 47 AA Brigade) |
Order of Battle February 1943
| 125 Light Anti-Aircraft Regiment (417, 418, 419 Batteries) |
| 1 Searchlight Regiment (1, 2, 7 Batteries – 8 Battery attached 71 AA Brigade) |
| 34 Searchlight Regiment (302, 337, 338 Batteries – 336 Battery attached 47 AA Brigade) |
| 73 (Kent Fortress) Searchlight Regiment |
| 355 Searchlight Battery from 39 Searchlight Regiment – disbanded May 1943 |
125 LAA Regt replaced by 4 LAA Regt early spring 1943. 4 LAA Regt left May 1943 leaving the Brigade searchlights only.
Order of Battle June 1943
| 1 Searchlight Regiment (1, 2, 7, 8 Batteries) |
| 33 (St Pancras) Searchlight Regiment (332, 333, 334, 543 Batteries) |
| 34 Searchlight Regiment (302, 336, 337, 338 Batteries) |
| 83 Searchlight Regiment (365, 513, 514, 515 Batteries) |
Order of Battle January 1944
| 1 Searchlight Regiment (1, 2, 7, 8 Batteries) |
| 33 (St Pancras) Searchlight Regiment (332, 333, 334, 543 Batteries) |
| 34 Searchlight Regiment (302, 336, 337, 338 Batteries) |
| 36 (Middlesex) Searchlight Regiment (317, 345, 346, 424 Batteries) |
| 38 (The King’s Regiment) Searchlight Regiment (350, 351, 352, 353 Batteries) |
| 61 (South Lancashire Regiment) Searchlight Regiment (432, 433, 434 Batteries) |
| 79 Searchlight Regiment (502, 503, 504 Batteries) – Oct 44 to 56 AA Brigade |
| 83 Searchlight Regiment (365, 513, 514, 515 Batteries) – Oct 44 to 56 AA Brigade |
In March 1944 all Searchlight Regiments were reduced to 3 batteries
