Not a Cromwell chassis, think bigger, what we see here is a 120mm gun. I wouldn't be surprised if that pic was from Bovington ... but they could have made a better one, it's dark and hiding a lot of details. Here is a much better one (don't look at the pic properties I just cross linked it): The final proposal's turret, with a really huge 183mm gun looked a lot like a KV-2.
The only thing bigger than a Cromwell chasis is a Centurion chasis, which this resembles slightly, though this is apparently the rear of the vehicle, which I must say I can be sure of. The side view you gave us first I think shows six road wheels, but the picture is so poor that I can only surmise there are six. There were a bunch of experimental AFVs built on the Centurion hull that were prototyped and tested in the 1950s, but isn't that post-war period out of bounds? Or am I mistaken?
Not as far as I know, the very first post on this thread was modern, we had a few moderm beasts from time to time though we try to stock to WW2 and earlier as most of us have more interest in that period. And yes it does have six roadweels. BTW the site this is comming from has some wonderful "oddies"
Well, that's definitely a Centurion chasis. I'm guessing an assault gun prototype from about 1955, the AV4004?
The FV 4004 Conway in all it's glorious ugliness, these were really tank destroyers not assault guns, meant to engage the feared soviet supertank hordes intelligence believed existed. We now know that reality was just the JS-10 that a standard L7 gunned Centurion could deal with. FV4004, 120mm Conway and FV4005, 183mm gun tank
We haven't had an answer for a while now so if anybody would like to post a pic then go for it as I will take the flak for the decision
Well looks like it's down to me then just to keep this great thread going I would like the full and correct name and a brief description of this vehicle View attachment 13781
Panzerkampfwagen IV Ausführung H/J. The H-model of this tank was introduced in 1943 and featured thicker armor to provide better protection against the Soviet T-34/85s and JS-IIs. It got the newer 7,5 cm KwK 40 L/48