trump thought the BBC was going to act just like the feckless American media that rolled over when he sued them and settled (mostly because most are now own by his friends). BBC isn't playing that game and saw their opportunity to nail him on discovery.

He first claimed they had caused him to lose money after they correctly reported he incited the attack on the US Capitol on Jan. 6. BBC said, ok, fine, show us your financials so we can determine what value loss you experienced.

At that moment, he knew he had screwed up, because he withdrew his claim that they had hurt him financially.

Now, BBC is subpoenaing his family to determine whether their documents shed light on whether their "alternation" of his speech changed it significantly or not.

That's why Trump is claiming harassment, because he knows they did not change it much and he did incite the violence, purposefully and it was part of his plan, along with the fake electors, and pressuring Mike Pence to violate his oath of office, to stay in power, despite losing, i.e. an autogolpe, or self coup.