I see the Guardian has a quotation from the session I have just described:

Labour also kept the pressure on Johnson. Keir Starmer, the party leader, said it was “extraordinary that the prime minister stopped the scientists being able to answer a question put to them by journalists”.

Answering questions on a virtual Q&A with voters, Starmer said this reflected badly on Johnson: “The government has been saying for weeks on end, this is about transparency, it’s about answering whatever questions you’ve got. And then on the question people want to hear an answer on, he stops them answering. It’s the wrong thing to do.

“I don’t think he’s going to have impressed anybody with that tonight. I don’t think he’s impressed anybody over the past week.”