When Donald Trump says, “A lot of people don’t know that” – or its rhetorical cousin, “People don’t realize” – he’s generally referring to things many people already know, but which he only recently learned.

As the Washington Post’s Dana Milbank noted last year, “Trump’s lessons are often accompanied by raised eyebrows, widened eyes and a ‘gee whiz’ look that suggests perhaps the nation is witnessing the president’s education in real time.”

There are, however, occasional exceptions. For example, Trump used the phrasing a couple of years ago to reflect philosophically. “People don’t realize, you know, the Civil War, if you think about it, why?” the president said in 2017.

But then there are the instances in which the Republican makes the declaration to make a point that’s false, but which he wishes were true. As regular readers may recall, then-candidate Trump insisted three years ago that “nobody knows” that the murder rate is at 45-year high. In reality, nobody knew that because it wasn’t true. Trump has also argued that “a lot of people don’t know” that U.S. taxes are the highest in the world, which would be fascinating, if his point weren’t completely wrong.

This morning, Trump added to his greatest hits collection with remarks to British Prime Minister Theresa May before a business roundtable discussion in London.

“We are your largest partner. You’re our largest partner. A lot of people don’t know that. I was surprised. I made that statement yesterday, and a lot of people said, ‘Gee, I didn’t know that.’ But that’s the way it is. “And there’s an opportunity – I think a great opportunity – to greatly enlarge that, especially now, in light of what’s happening, to tremendously enlarge it and make it a much bigger trading relationship. So we’re going to be working on that today and even a little bit tomorrow and probably into the next couple of weeks. But I think we’ll have a very, very substantial trade deal.”

Of course, “a lot of people don’t know that” that about the trade partnership because it’s not true.

At first, I wanted to give Trump the benefit of the doubt. When he said, “We are your largest partner. You’re our largest partner,” I thought it was at least possible that he was speaking more broadly about a range of issues, including matters such as national security. But in context, according to the White House’s official transcript, the Republican left little doubt that he was talking specifically about trade.

Which is unfortunate. The United States’ largest trading partner is China, while the United Kingdom’s largest trading partner is Germany.

I don’t seriously expect the American president to know that off the top of his head, but if Trump is going to travel abroad, I do expect him to avoid certain obvious falsehoods about his hosts. He shouldn’t travel to London, for example, and say, “We are your largest partner. You’re our largest partner. A lot of people don’t know that. I was surprised. I made that statement yesterday, and a lot of people said, ‘Gee, I didn’t know that.’ But that’s the way it is.”