It's a US federal court in Florida
https://share.google/j1xPrAt1Swvuec7bx
Damages awarded for libel/slander in UK courts are outsized super pay days, and many a foreign sheikh or business mogul has tried to establish that the matter under question was made known to UK citizens and therefore UK has jurisdiction, because the damages will beat anything awarded anywhere else in the World.
Weirdly, Trump has argued that this was damaging to his election chances (reminder: he won the election he's arguing about), and in a jurisdiction that the BBC can show the material wasn't available in, at least not legally and through their enablement.
As a result, even the BBC's critics in the UK (of which there are many), are seeing this as just a grifter trying to shakedown an organisation he doesn't like the reporting of, because he can't do it to a US network without getting into a first amendment quagmire.
In the UK, an alleged defamatory statement is presumed false and the defendant needs to prove it is true, and that burden is unusually low compared to most other jurisdictions, and certainly much lower than in the US where the burden is on the accuser to prove the statement is false.