There's not way you can beat Zammit at this game, it's got loads of wiggle room and in the end all his committee has got to say is "we don't believe you."
Which would, ironically, be rather like another million-squillion dollar bet...
Maybe so, in which case they are no better than the thing they have set out to bludgeon.
Zammit's challenge is impossible, since you can't prove a negative and most of the evidence either way is hearsay. A lot of the protagonists are dead.
It is not calling for the 'proof of a negative' - rather, the refutation of an argument (or set of arguments), which is perfectly within the bounds of possibility.
The fact protagonists are dead has no bearing whatsoever. If it did, history as a discipline would be...erm...history...
Hearsay is uncorroborated. A lot of the material presented has been corroborated by other testimony or experimentation. The hinge seems to be the rejection of testimony as evidence, which strikes me as a goal-post-moving gesture by those who wish to evade the debate (not suggesting you are such, Timble).
In fact, corroborated testimony is the basis of so much we accept without having experienced ourselves. When it is claimed an eclipse experiment corroborated Einstein on the curvature of space, I have to take the experimenters at their word; when it is repeated, I have to take the experimenters at their word....and so on...a point comes when I make a commitment and come off the fence because I see no reason to doubt their veracity, and what is being presented strikes me as worth taking on board, or is difficult not to take on board without entailing a chain of contradictions.
Zammit has his agenda, but he is serving to show how this topic has been dismissed prima facie, without due examination. Given the philosophical importance of the topic, this is remarkable.