The Field (S.P.) Battery was the meat of the Field (S.P.) Regiment, 1 of 4 artillery regiments (battalion-sized) allotted to each British Army Armoured Division's Royal Artillery. The others were the Field Artillery Regiment (with 24x towed 25pdr guns), Anti-Tank Regiment (with 24x towed 17pdr guns and 24x M10 or Achilles 17pdr tank destroyers), and Light Anti-Aircraft Regiment (with 54x 40mm anti-aircraft guns). Each Field (S.P) Regiment consisted of a Regimental Headquarters and 3 of these batteries. Meanwhile, each battery consisted of a Battery Headquarters and 2 Troops (each further consisting of 2 Sections).

What set the S.P. artillery apart were their use of self-propelled platforms built on tank chassis, which gave them identical or better cross-country mobility to the tank and mechanized infantry units they would be supporting. The main standard was the Sexton 25pdr self-propelled gun, which replaced the American M7 Priest 105mm self-propelled gun by August 1944. The M7 Priest had been introduced more or less as a stopgap to replace the Bishop 25pdr (based on the Valentine infantry tank chassis) because of that SPG's issues, but the British wished to move over to their own indigenous design. Thus came the Sexton. Although only partially indigenous (since it was based on the Canadian Ram, which was itself a derivative of the American M3 tank chassis), it freed them from reliance on American supply chains to maintain and replace their SPGs. War Establishments from early 1944 still specifically call for 105-mm S.P. mountings (referring to the Priest), however, and Priests were used on the first day of the Normandy landings (fired from landing craft no less). However, these Priests were quickly replaced with the Sexton a few days after the landing to standardize British artillery ammunition in-theatre (since British towed field artillery regiments were on the 25pdr standard). Our graphic associated with this article shows the Sexton 25pdr, but ammunition figures in the Organization section mostly refer to Priest-equipped units as they were accounting for the 105mm standard. Priests shells (105mm calibre) were larger than Sexton shells (88mm calibre), so generally speaking it could be assumed each ammunition vehicle could carry more shells in Sexton-equipped units. Alternatively, fewer lorries may have had to be used to carry ammunition, although we don't have sources on what the actual outcome of the switchover was vis-a-vis ammunition supply.

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As for the organization, the Battery Headquarters was split into a Command Portion and an Administrative Portion. The former consisted primarily of the Battery Commander in an armoured observation post and a battery command post, while the latter was mainly concerned with supplying the battery with ammunition, POL (petrol, oil, lubricants), food, and water, as well as some second-line maintenance.

In British artillery tradition, the Battery Commander (a Major), was originally the battery's sole observer, although by World War II Troop Commanders had also gained this responsibility. A key difference between American and British practice is British observers are officers that order fire from their guns — being in command of the unit they were ordering fire from — rather than requesting fire from an officer in the fire direction center. In this capacity, they'd act either as Forward Observation Officers (FOO) or Observation Post Officers (OPO) co-located with the CP of the Motor Battalion (mechanized infantry) or Armoured Regiment they were supporting. For this reason, Battery Commanders and Troop Commanders were equipped with either Armoured Observation Posts for the former and Tank Observation Posts for the latter. These basically amounted to Canadian Ram or American Sherman (75-mm gun variant) tanks outfitted with extra communications equipment. Typically the policy was to match the tank of the armored unit the battery was supporting (mostly Shermans or Cromwells by the late war), although non-standard tanks like the Ram and others were used when necessary. Although these were officially meant to be issued with their main armament intact, dummy gun Shermans (with fake guns made out of wood) or Shermans with their breechblock removed were sometimes used to allow for the stowing of additional communications equipment. The logic goes a normal looking tank is a less appealing target than a tank that looks special, so removing the gun altogether was undesirable.

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Back at the Battery Command Post, there were 3 officers. The Battery Captain was essentially a Battery 2IC and was more administrative in nature, uninvolved with the control of the battery's firing. Meanwhile, the Command Post Officer (a Subaltern) actually directed the battery's firing and local defense. They were assisted by an Assistant Command Post Officer (also a Subaltern). The CP was staffed by a heaping helping of Signallers (radio operators), a Signalling Serjeant (in charge of battery signals), an attached Electrician (REME), and motorcycle orderlies (essentially messengers). As always, every officer had a Batman or officer's servant, who was essentially a personal assistant to each officer, although these were mostly contained in the Administrative Portion of the Battery HQ.

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The Administrative Portion as previously mentioned was the battery's sustainment section led by the Battery Quarter-Master-Serjeant (ranking Staff Serjeant). Other than how the guns of the battery were organized, the magnitude of the Battery HQ's train was probably one of the biggest differences between the British S.P. Battery and the American Armored Artillery Battery. During World War II, the British had a propensity for putting more of their train in the company/battery HQs than the Americans for example. Whereas the Americans would keep most of its sustainment at battalion-level, the British didn't earmark any Regimental HQ trucks for the carriage of artillery ammunition. Thus, basically the entire battery's ammunition supply was in the battery train for the British case. This also extended to petrol tankers. The main exception was in medical support, which was held and supplied at the regiment-level. 

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Now for the Troops. Each battery had 2 Troops, each with 4 guns (8 guns per battery). The Troop consisted of a Troop Headquarters and 2 Sections, each Section equipped with 2 S.P. Mountings. The S.P. platforms were referred to as Sub-Sections or "Subs" colloquially. 

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The Troop overall came under the command of a Captain, who rode in a Tank Observation Post with a crew and an Observation Post Assistant. As with the Battery Commander, the Troop Commander's vehicle would have either been a modified version tanks identical to those they were supporting (or a different model if needed). With this, Troop Commanders acted as the troop-level forward observer, directing his troop's guns onto target. Also equipped with a Tank Observation Post was the Gun Position Officer (GPO) who was a Subaltern located with the Troop CP when deployed, although these would be replaced with Canadian Ram carriages (similar to a Sexton without the armament or the Kangaroo APC) by the end of the war. For the Troop Commander, protection was more important being closer to the frontline as an observer, while the GPO mainly needed a platform with the same mobility as the guns they'd be directing.

GPOs were the senior officer at the Troop CP and responsible, along with the Battery Command Post Officer, with positioning the guns for firing, receiving fire orders, and ensuring the troop's guns were aimed correctly. However, if the Battery was firing as a single unit, the Battery Commander could also order fire from one officer in one of the Battery's OPs who would then calculate and coordinate the fire of all the battery's guns. The Troop Leader, another Subaltern, was the most junior officer of the Troop. Usually the Troop Leader would be tasked with leading the Troop's non-combat supply vehicles, which would be located out of harms way when in combat and could be brought up to resupply the Troop as required. In other circumstances, they were used as relief for the GPO or the Troop Commander. Ideally, most of the battery's officers and senior non-commissioned officers would be trained on each other's tasks so they could relieve each other if needed. Meanwhile, the Troop Battery Serjeant-Major (Trp BSM) was essentially an equivalent to an infantry Platoon Serjeant.

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As for the guns themselves, each S.P. Mounting was manned by a gun crew of 5 (Priest) or 4 (Sexton) and a 2-man vehicle crew. The gun crew was commanded by a Serjeant (designated No. 1 during drills). The No. 2 operated the breach, No. 3 laid the gun, No. 4 loaded, and No. 5 handled ammo. It is possible that on the move over to Sexton SPGs that the No. 5 was deleted. Most of these men would have been Gunners (equivalent to Private outside of the Royal Artillery), although 1 or 2 could be Bombardiers (equivalent to a Corporal) or Lance Serjeants. The most senior would be designated as the gun crew's second-in-command. The vehicle crew then consisted of a Driver-Mechanic (A.F.V.), who was the proper vehicle driver, and a Driver-Operator, who manned the wireless.

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In terms of capability, the Sexton's 25pdr gun had a range of about 12.2 kilometers while the Priest's 105-mm could reach out to 10.4 kilometers (probably limited by restricted elevation on the vehicle-borne platform). HE projectile weight on the Priest was 14.97 kg (33 lbs) while the Sexton's was 11.3 kg (24.9 lbs). Broadly speaking, the British Army's rate of fire standards were the same for both platforms. Five rounds per minute was considered "Intense", 4 rpm was "Rapid", 3 rpm was "Normal", 2 rpm was "Slow", and 1 rpm was "Very Slow". Calculating the ammo carried on hand (assuming the use of 105-mm gunned Priests), each S.P. mounting carried 69 rounds (552 rounds battery-wide), each Section half-track carried 44 rounds (176 rounds battery-wide), and Battery HQ trucks and half-tracks carried a combined total of 648 rounds. That makes 1,376 rounds carried on-hand by the battery, 172 rounds per gun (about 2.5 units of fire), or about an hour of sustained fire at the "normal" rate of fire for the whole battery. This was likely higher in Sexton-equipped batteries due to the smaller ammunition.

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