IANAL, but I think the answer is "both." You can sue in the country it was created in, but if the video also aired in the US on BBC or other services here, the suit can happen in the US as well. 

(That said, libel penalties are generally harsher in the UK, so most folks choose that option.)

StillStackinAfterAllTheseYears

Politics_And_Law

Explain like I am five. How does the law work here? 

BBC doctored a video of Trump, and he is apparently going to sue them for reputation damage. But which court can or should handle the case? The UK Supreme court or SCOTUS? 

Would Trump have to hire UK lawyers to represent him? If so, would not those lawyers' actions be perceived as treason against their own nation and siding with a foreign president (who is also hated by most Brits under Labour)? 