Vickers tank with Recoilless rifles and a .50 cal?
ONTOS in Viernam that is.
EDIT:
I do not know if this is real or not, but i seriously doubt that everything went to plan here. I mean, those people in the back seem a tad to close to that rather big explosion.
It's real alright and you're very right about things not going to plan.
During Operation Granby a Centurion AVRE was said to have caught fire which then spread to the munitions, resulting in the massive blast you see here. The fact that it caught fire meant that people were able to try and escape and as a result there were, amazingly, only 4 minor injuries from the blast.
A rumour was that the crew were cooking breakfast on the engine deck. Not a great way to start your day if that's true!