Robberies have increased significantly in London from 2016 to 2019, and knife crimes are also a concern, but “all violence seems pretty stable,” said Brian Francis, a statistician who specializes in criminology at Lancaster University. For a comparison, Mr. Francis noted that violent crime in Manchester, England, nearly doubled in that same period.

The Crime Survey for England and Wales, a metric of crime used by the Office for National Statistics, shows that violent crime has not changed significantly relative to the start of Mr. Khan’s term. By that measure — which, unlike reported crime, is not influenced by reporting rates of incidents unnoticed by the police — London’s violent crime rate decreased to 14 incidents per 1,000 people in 2017 from 19 incidents per 1,000 people in 2016, before returning to 19 incidents per 1,000 people in 2018.

The police recorded that crime grew by 3 percent in London from December 2017 to December 2018, compared with 7 percent across England and Wales. London’s total crime rate of 95.4 per 1,000 people in 2018, per police data, is above the national average, but below the rates of several other areas, like Manchester (119.7), Cleveland (115.5), Lancashire (109.2) and Kent (107.6). London’s violent crime rate was below the national average, though its theft and robbery rates were the highest across the country.

What TRUMP Said

“I said, ‘Where are the protests? I don’t see any protests.’ I did see a small protest today when I came — very small. So a lot of it is fake news.”

— News conference with Prime Minister Theresa May in London

False.

Mr. Trump’s calling protests in London “fake news” contradicts photographic and video evidence.

Attendance was lower than the protests during Mr. Trump’s visit to Britain last July, but still sizable. Protesters gathered in Trafalgar Square, outside Buckingham Palace and in Parliament Square, among other locations in the city. Organizers estimated a turnout of 75,000 on Tuesday, while news reports — including Mr. Trump’s preferred outlet, Fox News — have cited thousands of participants.

What Trump Said

“I really predicted what was going to happen. Some of you remember that prediction. It was a strong prediction, made at a certain location on a development we were opening the day before it happened.”

— News conference with Prime Minister Theresa May in London

False.

While Mr. Trump did make statements about Brexit before the referendum, the one he was referring to occurred afterward. He said, “I think that Britain will separate from the E.U.” But that comment occurred in March 2016, and not at the location he was referring to.