The Matilda Hedgehog is a rather interesting development of the A12 Matilda 2 infantry tank. Having been retired from service after the Allied victory in North Africa a number of these indomitable old machines ended up shipped to Australia, mostly they were the close support versions with 3 inch tank howitzers and they gave dependable service against the Japanese, who by and large had nothing much that could penetrate their heavy armour.
The Australian army however felt that the basic Matilda wasn't meeting their needs when it came to firepower for dealing with Japanese forces in bunkers. The Matilda hedgehog was basically a standard Matilda 2 hull with a compact version of the Naval "Hedgehog" anti-submarine projector mounted to the rear of the hull above the engine.
This weapon was basically a spigot mortar like the infamous PIAT anti-tank launcher, although much larger. While only firing 7 rounds compared to the 24 of the naval version the Matilda hedgehog was still a devastating bunker buster at short ranges. The main drawback being that reloading of the hedgehog launcher had to be done from outside the hull, so the vehicle would need to retire to reload before it could be used again.