LONDON — Scientists faced a “real struggle” in trying to get Boris Johnson to understand key terms and statistics relating to coronavirus, Britain’s COVID-19 pandemic inquiry has been told.

Extracts from the contemporary diary of Patrick Vallance — the government’s chief scientific adviser during the pandemic — claim that on several occasions Johnson, then the prime minister, was confused and “bamboozled” when engaged in conversations about the virus.

“Watching PM get his head around stats is awful,” one extract from Vallance’s diary, dated June 11 2020 and read out at the inquiry Monday, reads. “He finds relative and absolute risk almost impossible to understand.”

Johnson was “taken through the graphs but it was a real struggle to get him to understand them,” another entry from February 2021 reads.

A third, from May 2020, said Johnson was “clearly bamboozled” by what Vallance described as a “complicated” meeting on the risks and science behind the question of reopening schools.

In another entry from September 2020, Johnson is said to be surprised to see a chart illustrating “all the same stuff he was shown 6h[ours] ago.”

Giving evidence to the inquiry in person Monday, Vallance said his former boss would be “the first to admit” that scientific concepts are not his forte. Vallance said fellow scientific advisers in Europe had often complained to him of a lack of scientific understanding among their own leaders.

“But it was hard work sometimes to try and make sure that he had understood what a particular graph or piece of data was saying,” the top scientist continued.

“I would usually be persuaded that we had got him to understand what it was we were trying to say. But as one of the extracts showed, six hours later he might not have remembered what was in that presentation — so I can’t be sure that he kept in his mind all the time,” he added.

Johnson will appear before the inquiry to give evidence in the next two weeks.

Earlier Monday, Vallance argued that the government failed to act quickly enough to deal with the pandemic in its initial phases. Asked about the early stages of the pandemic as cases began to rise in the U.K, Vallance said researchers had realized an estimated 75 percent reduction in contacts between individuals would be required to prevent the National Health Service becoming overwhelmed.

“I am not convinced that there was a very effective operational response to that,” he added.