What do we know about the Covid-19 lab leak theory?

The origin of Covid-19 still eludes the scientific community, but the FBI's assertion that Covid-19 most likely originated in a Chinese government-controlled lab has ramped up the debate.

The FBI's position runs contrary to some other US government agencies, some of whom have said, with a low level of certainty, that the virus did not start in a lab but instead jumped from animals to humans, possibly in Wuhan's seafood and wildlife market.

Now the World Health Organisation has responded saying that until they have conclusive evidence, all hypotheses are on the table.

What evidence do we have of how the pandemic spread so fast and so far? Newsnight's David Grossman reports.