A BBC Video Diary programme wanted to film Maurice [Grosse] attending an investigation. ASSAP organised one such event at Charlton House and a cup was caught exploding in a darkened room on video in a locked room with a camera man, Maurice and one other investigator witnessing it. BBC Radiophonic Workshop tested the sound patterns and concluded that it was NOT the sound of a cup being broken in the usual way and further experiments failed to replicate the circumstances. It seemed to implode rather than explode.
In my tribute to Maurice Grosse that I posted a couple of years ago, I linked some videos of the opening segments of that Video Dairies program. To my knowledge, the second half of the show, which includes the material Melvyn refers to, wasn't available on YouTube at the time. But the full program was recently put up, which I saw linked on the Twitter account of the Society for Psychical Research (SPR). Go here to see the beginning of the relevant segment of the program. The event in question happens at 32:12. After the event, you see some discussion of what happened among the people there at the time and a discussion among some members of the SPR's staff. (Including an argument between Grosse and Mary Rose Barrington, accompanied by a cup-throwing experiment in the SPR's facility!) There's then some intervening material on other subjects, so you can go here to see the remainder of what's relevant to the topic of this post.
For further background about Charlton House and the event under consideration here, read this article at the Occult World web site. I want to quote some comments Guy Playfair made about this incident, then conclude with some comments of my own: