First Lady Melania Trump makes surprise drop in at Salvation Army in London

First Lady Melania Trump has been serenaded a Mariah Carey Christmas classic during a surprise drop in on her visit to the UK for the 70th anniversary NATO summit.

London children sang "All I Want for Christmas is You" after Melania Trump popped in to help them make wreaths and ornaments at a Salvation Army centre in London.

At the facility in the Clapton neighbourhood of East London, Mrs Trump helped attach pine cones to a wreath covered in yellow tinsel. She also helped US Marines put gifts into holiday-themed bags.

The First Lady nodded in apparent enjoyment as the pupils serenaded her, then clapped and appeared to say "bravo" when they finished the song.

She also suffered some characteristically honest evaluations from the children who said she was much nicer than she appeared in photographs.

First lady Melania Trump joins local school students at the Salvation Army Clapton Center in London. Photo / AP

Isabelle Bates, 10, told the Daily Mail: "Everyone was asking her random questions, what do you do for Christmas and that."

"We were talking about mince pies and she said she never had one but she was going to try one tonight. I thought she was really fun."

"My impression of her was really nice. Everyone was expecting her to be grumpy but she was really nice.

"There was a picture in school we saw and we were looking at it and she looked really grumpy. But she wasn't."

We're all having fun. Photo / AP

Her friend, Quiana Mullings, nine, said: "I'm gonna be honest and say her make-up was a bit much.

"It made her look sad but actually she was very happy."

Mrs Trump also donated presents for the charity's holiday drive, including white baseball caps, white frisbees and soccer balls all stamped with the logo of her "Be Best" youth initiative. She gave the kids "Be Best" ornaments as gifts before she departed.

It came after her husband made headlines by taking high-profile swipes at French President Emmanuel Macron and Canadian Prime Minister Justin Trudeau.

The Trumps left London early after the US leader cancelled his final press conference.