Bryan Adams has spoken for the first time about how his friendship with Princess Diana was sparked by a song he wrote about her doomed marriage.

The singer recalled how the late royal said she found the lyrics about him "losing his mind" on the day she married Prince Charles "very funny".

Speaking to the Sunday Times, Adams added that Diana invited him round for tea so she could hear the song again.

He retired the song when she died in 1997 "out of respect", he added.

The 64-year-old Canadian's friendship with Diana led to some speculation in the 1990s that they had an affair, and this intensified in 2003 when his ex-girlfriend Cecilie Thomsen told reporters that "ours was a stormy relationship and Bryan's affair with Diana didn't make it any easier".

Adams has never responded to the rumours and does not discuss it in this interview. Instead, he reveals the pair "had a lot of really, really good conversations" as their friendship blossomed.

"In fact it's strange and surreal to think about. I really, really liked Diana, she was an amazing woman and a super-great inspiration," he said during the interview.

"Meeting her was truly one of the greatest things that ever happened to me."

He said the pair met on a plane, where he told her he used her name on a song and she responded: "Yes, I know, very funny. Actually I'd like to hear it again."

Adams sent a copy to Kensington Palace and she then invited him round for tea.

"When I first went round to KP (Kensington Palace) she wasn't, like 'I really need to talk to somebody', and you don't bulldoze into someone's life wanting to know everything in the first 10 minutes," he said.

"It was 'let's have a cup of tea'. But later the more friendly we got the more I learnt what was really going on."

Diana married Charles, now King Charles III, in 1981 and they had two sons together, Princes William and Harry. But after a marriage that was largely acrimonious in its latter years, the couple separated in 1992, before divorcing in 1996.

Adams made his big breakthrough in the UK charts in 1985 with five Top 40 hits - Run To You, Somebody, Summer of 69, It's Only Love and Heaven. The song Diana was the B-side to Heaven and its lyrics quickly caught the attention of the media.

They include the lines: "The day that he married you - I nearly lost my mind" and "Diana - what cha doing with a guy like him". Dropping a royal reference, Adams sings Diana is "the queen of all my dreams".

The husband of the Diana referenced in Adams' song clearly did not impress the singer-songwriter as he penned the lyrics: "He might have lots of dough; but I know he ain't right for you" and added: "You've got one choice - you can get away. Leave it up to me. I'll bring the ladder - if you bring your limousine."

But Adams called the lyrics "laddish humour" during the Sunday Times interview, adding he was actually inspired by "that guy who [had] broken into the Queen's bedroom and sat on her bed smoking a fag".

In 1982, the late Queen Elizabeth II woke up one night and found painter and decorator Michael Fagan sitting on her bed after breaking into her bedroom.

Adams had his biggest UK hit with his power ballad (Everything I Do), I Do It For You, in 1991.

His most recent album, So Happy It Hurts, reached number three in the UK charts last year.

But he has also been a keen photographer over the years and once took an official portrait of Queen Elizabeth, which then became a 49 cent Canadian postage stamp.

And in 2014, Diana's youngest son Prince Harry attended an exhibition of Adams' photographs while he was a British Army captain, as they featured images of injured veterans from the wars in Iraq and Afghanistan.

In the Sunday Times interview, Adams also talked about trying to help the late British singer Amy Winehouse during her battle with drug addiction in 2007.

He said he became friends with Winehouse after photographing her and he invited her to spend Christmas with his family at his villa on the island of Mustique.

He recalls trying to serve her a diet of carrot and beetroot juice, as well as vegan food - which she was not impressed with. And she also reportedly swallowed £2,000 worth of heroin wraps on the flight there.

When asked whether he thought he could save her, Adams said he "tried to help her but, you know, it's got to come from within".

"I really don't know what happened with Amy and it is so sad because she was so, so talented and I so admired her individuality massively. But did I make a difference? I don't know," he added.

In 2011, Winehouse was found dead in her flat in Camden, London.