Inside Queen Elizabeth's long history of meeting US presidents

Her Majesty will host President Trump and his wife at Windsor Castle this week.

ABC News’ Eva Pilgrim spoke with ABC News Royalty Consultant Alastair Bruce about the history and importance of the U.S.-U.K. relationship, what the queen is like as a hostess, and of course, what they might serve for tea.

Has Queen Elizabeth met with every president since she ascended the throne in 1952?

Alastair Bruce: Lyndon Johnson she didn’t manage to meet. But, you know, for the queen, who’s been head of state since she was 25, and she’s now in her 90s -- every president has had the chance to meet with her and she with them. Because the relationship between the United Kingdom and the United States is so strong.

The queen and President Trump will meet at Windsor Castle. How do logistical challenges affect royal-presidential meeting locations?

Bruce: I think there tends to be a very precise way of locking down a large number of streets in order to protect the president of the United States, and we don’t do that so much here in the United Kingdom.

And so I suppose sometimes it’s made sense, like when [President] Ronald Reagan came, and when [President Barack] Obama came on his last visit, to go to Windsor Castle because it’s in the middle of nowhere. It’s the queen’s sort of very special place. And yet it’s such an incredibly ancient and historic castle in its own right.

What is it like for the queen to open her home and let world leaders into her life?

Bruce: Her life is a very different kind of life because she is the queen of this country and she can never not be that, and so it’s always been part of her existence that she interacts with this sort of person.

When she was young, [President Dwight] Eisenhower was here in Britain, commanding the Allied troops about to go to D-Day. And the king, her father, said to him, 'Do you want to go and have a look around Windsor Castle?' So, then a few weeks later, the king and queen were actually in the garden. They heard voices coming. And the king remembered, 'Oh my goodness -- Eisenhower is coming!'

They didn’t want to embarrass him, so the king and queen and the two princesses -- that includes the [current] queen -- hid behind a hedge 'til they were gone. [They] didn’t want Eisenhower to feel uncomfortable.

How will President Trump and the queen spend their time together?

Bruce: We believe that the President will go and have a cup of tea with the queen. You see, you couldn’t do anything more British than that.

How formal will their meeting be?

Bruce: The queen is completely relaxed. If you’re a guest of hers, she will put you at her ease. And she makes the tea herself, and she will pour him his cup of tea and they can have a jolly good gossip.

You know, the queen’s never been brought up with too much deference. She is queen, but she gets on and does things for herself in the way that you do and I do.

The thing about the queen is that she is terribly relaxed with people. She’s a bit shy, I would venture. But you know, she’s met people all her life.

And she’s got this trick -- she never asks a difficult question.

Will they be alone?

Bruce: There will be dogs around. You see, the queen loves her dogs, and they will be around at tea, and she will be able to use the dogs to make sure there’s something to talk about.

What is the significance of the U.S.-British relationship to the strength of the monarchy?

Bruce: Well, you’re speaking English, and I’m speaking English. And it reminds us of that link, despite the fact that we’re divided by this massive ocean, our histories go back -- I mean, it hasn’t always been easy.

And the queen is forebear. [King] George III was head of state when the break between the colonies and this mother country of Great Britain occurred. And the queen, of course, carries on that office of kingship that George III had.

And yet, all that aside, when you think what the nations have been through, not least the defeat of Hitler in the 1940s, I mean that was a huge battle for everyone.

What have the queen's past meetings with U.S. presidents taught you about her?

Bruce: Just look at how comfortable the queen is in situations like that. When you have the visit by President Obama last time, and his wife, they were met by the queen and Prince Phillip in a car that the two of them were driving. You know, this was a very comfortable way of welcoming a president and his wife, and that probably doesn’t always happen to presidents of the United States. It’s normally much grander and more formal.

But the queen and the Duke of Edinburgh were welcoming the Obamas because they were on their own territory, their own home. And they met them with their car and said, 'Push over, you know, you get in the back.' And the queen was in the back of the car, and the Duke of Edinburgh drove them to the castle.

The queen knows that she is doing this for the United States. She knows that she’s welcoming President Trump on behalf of the United Kingdom. And that’s a really important role.

It’s a great privilege for her too. And you know, Britain’s got this amazing history bringing the head of state of our oldest ally into that environment. You know, it’s part of what the queen does.

Editor's note: This interview has been edited and condensed for clarity.