Hi Mike,
After the disaster of the Dieppe landings the British realised that in order to have any chance of breaking through beach defences they would need specialised equipment to deal with the Pill Boxes and obstructions.
A range of vehicles were developed based on the Churchill Mk III and Mk IV to meet this need and colllectively were known as the 'Funnies'.
Major General Hobart was an out spoken Offcier who in 1934 as Inspector of the R.T.C agigated for modernisation of the obsolete armoured divisions. He got retired.
However, he joined the Local Defence Force at the outbreak of war as a Lcpl but soon became Deputy Area Organiser of the re-named Home Guard.
Churchill was keen on his ideas for armoured warefare and he got re-instated and was initially given command of training the newly formed 11 Armd Division. When 11th Armd became operational he was given command of 79th Armoured Division which had been formed in 1942.
79th being the youngest Division got the task of this proposed assault role and the development of specialiased armour to meet this need.
The AVRE was one of many Funnies designed and trialed for the D Day Assault. This particular tank was fitted with the Spigot Mortar which fired an explosive charge the grand distance of 80 yds. The charge known as a dustbin was designed to blow holes in the sea wall defences, demolish bunkers and pill boxes. In effect it provided armoured engineers to deal with the fortifications which the Allies new they would face. The crew were engineers and could operate outside the tank as normal engineers if necessary.
It was the use of these Funnies that helped keep the British and Canadian losses down during the initial landings and allowed them to breech the sea walls, anti-tank ditches and deal with fortifications that otherwise would have casued havoc to the landing troops and tanks.
Like the Mulberrys and the pipelne across the channel these vehicles went a long way to breaking the Atlantic Wall and continued in their Assault role until wars end. 79th Armoured Division was effectively an Assault Armoured Engineer Division.
The Americans only adopted two of the Funnies the Flail Tank and the DD SHerman. Had they had armoured engineer support on their landing beaches well who knows......
Hope that potted history helps a bit.
Al