Elsewhere, the former education secretary said he regretted the lack of planning that went into school closures at the start of the pandemic.
“I readily accept that there were many mistakes that were made,” he said.
He apologised to the inquiry for failing to pay more attention to scientific evidence published in February, which suggested school closures could delay or reduce the peak of the pandemic.
The government should have “bitten the bullet” and made a plan for school closures, he said, adding that he had made an error by “sticking with the plan” to keep schools open, as that was the focus of the government in March 2020.
It was only overnight on 17 March 2020 that a plan was put together to close schools, before an announcement was made the next day.
“I regret that and wish we had very much done it differently,” Williamson told the inquiry.
“But we were at the time acting in what we believed was the best interest and under the best guidance.”
He also said it probably would not have been “allowed” to start preparing for the closure of schools without approval from Downing Street.
“Something like Covid is being directed from the centre, in terms of different departments’ responses,” he said.
“You don’t have quite the freedom just to go and start going out and consulting with lots of people.”