Vermuelen's testimony - direct exam:
Oscar Pistorius Trial: Wednesday 12 March 2014, Session 1 - YouTube
At around 40:45 - 43:45 Vermuelen testifies that the cricket bat was used to bash the door and that the cricket bat broke through the door with one of the hits. If you keep watching, he says he only found 2 cricket bat marks.
Vermuelen cross exam:
Oscar Pistorius Trial: Wednesday 12 March 2014, Session 2 - YouTube
4:25 Nel says that it's his case that OP was not on his prostheses when he fired the shots
Vermuelen further cross exam:
Oscar Pistorius Trial: Wednesday 12 March 2014, Session 2 - YouTube
At 52:46 the following exchange between Roux and Vermuelen:
Vermuelen also says that when the cricket bat hit the door and broke through it, the cricket bat was then used to pry open the panels from the door