The BBC obviously fucked up and the programme shouldn't have been edited in a way that was likely to mislead viewers about what Trump had said and when. However, I really don't understand how Trump would have a chance of winning a defamation case.
Firstly, from what I understand, he would need to sue in the US (Florida?), because he would be out of time to sue in the UK. And I gather that the programme wasn't even broadcast in the US, so that's presumably a significant hurdle.
Secondly, if he is claiming damages, what's the evidence of any actual damage having been done? The BBC weren't the first to suggest that he incited the Jan 6 riots, he had actually already been indicted in the US for his part in trying to subvert the election result. So while the spliced video was misleading about the specifics of what was said, it didn't point to any overarching allegations that weren't already in the public domain. Plus Trump was elected soon after the programme aired, so it isn't at all clear that it actually damaged him in any way?
Thirdly, I understand that under Florida law, Trump would have to prove that the BBC had malicious intent. I can't see how he would evidence this, particularly given that the rest of the panorama programme was actually quite balanced and included material that was favourable to Trump.
Defamation implies that the BBC causes damage to Trump's reputation. But Trump already had a terrible reputation and had already been accused in the US of inciting the riots. So while the BBC edit was grossly inappropriate, unprofessional and damaging to the BBC's reputation, I struggle to see how it did any damage whatsoever to Trump. So I struggle to see how he could win this case. I would love for someone to explain why they believe the courts might reach a different conclusion, and on what grounds etc.