Whereas most German wartime tank designs were repeatedly upgraded so they  remained viable fighting machines, the British were rarely able to do the same. The  Churchill was an honourable exception, and went through 11 marks and numerous  specialized derivatives.

The Churchill itself was the ‘Infantry Tank Mk IV’ producing some rather clumsy nomenclature – a Mk III Churchill was strictly an ‘A22 Infantry Tank Mk IV Churchill III’.

Mk I: 2-pdr gun and coaxial Besa MG in a small cast turret, with a 3in. howitzer in the hull. A few were built as Close Support versions, with the 2-pdr and howitzer swapped around.

Mk II: 3in. howitzer replaced by a second hull Besa.

Mk III: 6-pdr and coaxial Besa in a new welded turret.

Mk IV: New cast 6-pdr turret but otherwise as the Mk III.

Mk V: Close Support variant of the Mk IV, with 95mm howitzer in the same turret.

Mk VI: Effectively a Mk IV with 75mm gun. Strictly, only new-built 75mm vehicles are Mk VIs, and those converted are Mk IV (75mm) but functionally identical.

Mk VII: An extensive redesign with slightly wider hull, maximum armour thickness increased from 100mm to 152mm, and round rather than square side escape hatches. A new composite cast and welded turret mounted a 75mm gun, and vehicle weight increased to 40 tons.

Mk VIII: Close Support version of Mark VII with 95mm howitzer.

Mk IX: A conversion of existing Mk III or Mk IV 6-pdr tanks fitted with a Mk VII turret and appliqué armour plates bringing it to Mk VII armour standard.

Mk X: Equivalent conversion of existing Mk VI 75mm tank to Mk VII armour standard.

Mk XI: Equivalent conversion of existing Mk V 95mm Close Support tank to Mk VII armour standard.

The three ‘upgrade’ marks were also to be produced as ‘Light Turret’ (LT) versions, retaining their original turrets. At least 33 Mk Xs were created, but there is little to suggest any Mk IX or XI conversions were actually carried out.

An ‘all round vision cupola’ replaced the original traversable commander’s periscope partway through the Mk VII production run, giving commanders much better situational awareness without exposing their heads.

The exposed tracks of early Churchills kicked up a lot of dust, so track guards were added from the Mk III onward. Crews sometimes removed the centre sections, since they could become packed with mud or even jam the turret if damaged by enemy fire or when crashing through hedges.

Churchills also served as the basis for numerous specialized vehicles, including an unsuccessful tank destroyer – the Churchill 3in. 20cwt gun carrier – mounting a high-velocity 3in. antiaircraft gun in a fixed mount.

The Churchill Crocodile was a Mk VII with its hull machine gun replaced by a flame projector with a 120yd range, fed from an armoured 400-gallon fuel trailer towed behind the vehicle. Crocodiles were terrifying psychological weapons, and very effective against bunkers, as the burning fuel penetrated any apertures and consumed all oxygen in enclosed spaces.

The Churchill Armoured Vehicle, Royal Engineers (AVRE) replaced the standard gun with a short-ranged 290mm ‘Petard’ Spigot Mortar for destroying bunkers and concrete beach defences. AVREs could also carry a variety of obstacle-breaching equipment, including fascines to fill ditches and ‘Bobbins’, which laid canvas trackways across patches of soft sand on the invasion beaches. Two squadrons (26 AVREs each) landed in the first wave on each British D-Day beach. Aside from their engineering role, they provided valuable fire support for the first infantry units ashore, since the amphibious Sherman DD tanks were delayed by heavy sea conditions and many were lost.

Wartime AVREs were based on Mk III or MK IV hulls, but post-war versions were based on the better-armoured Mk VII and replaced the petard with a 165mm demolition gun, remaining in service until 1965.

The Churchill Armoured Recovery Vehicle (ARV) was a turretless version intended to recover damaged tanks for repair and fitted with an A-frame jib to facilitate engine changes. The Mk I version simply carried a repair crew and towed damaged vehicles, while the more capable Mk II had a fixed ‘turret’ superstructure with a dummy gun containing a 25-ton recovery winch.

Numerous bridge-layers, ramp carriers and other specialized engineering vehicles were also based on the Churchill, but space precludes consideration here.

You can read more in  DUE 118 Tiger vs Churchill: North-West Europe, 1944–45.

Churchill Mk IV