191 (Hertfordshire & Essex Yeomanry) Field Regiment RA was formed from personnel in 86 & 147 Field Regiments in December 1942 with three batteries. Each Field Regiment supplied a batteries worth of men, the remainder coming from disbanded Infantry Battalions. The Regiment served in the UK and North West Europe. 191 (Hertfordshire & Essex Yeomanry) Field Regiment RA was disbanded in January 1945.
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.
| Dec 42 | Formed from 86 & 147 Field Regiments | Slingsby, Yorkshire, UK | |
| Dec 42 | Home Forces | UK | |
| Mar 43 |  |
42 Armoured Division | Trowbridge, Wiltshire, UK |
| Oct 43 |  |
2 Canadian Army Group RA | Sutton, Surrey, UK |
| Apr 44 |  |
2 Army | Billericay, Essex, UK |
| Jun 44 | |
2 Army | Normandy, France |
| Sep 44 | |
4 Army Group RA | Le Havre, France |
| Oct 44 |  |
1 Corps | Turnhout, Belgium |
| Nov 44 | |
1 Corps | Etten, Holland |
| Jan 45 | Disbanded |
Batteries
| Dec 42 | 532, 533, 534 |
Equipment
| Feb 43 | 533 & 534 – 25 pdr Guns, 532 – 18/25 pdr Guns |
| May 43 | 24 x 25 pdr Guns |
| 1943 | Crusader Mk3 Observation Post tanks later replaced by Cavaliers. OP tanks were removed in May 44 and then loaned by the supported formation. |