Kate Middleton's colourful uncle Gary Goldsmith has told Hello! magazine that he will play a part in the upbringing of the baby of his niece and Prince William.

Goldsmith said he was planning to write his memoirs and has given a tell-all interview to the celebrity magazine about his relationship with the Duke and Duchess of Cambridge.

How much Kate's uncle was paid for the interview has not been disclosed, although the magazine has been known to pay great sums to its interviewees in the past.

Four years ago Goldsmith, 47, was caught up in a drugs scandal after journalists filmed him taking cocaine and saying he could arrange drug deliveries.

Despite his indiscretions, the Middleton's invited Goldsmith to their wedding in 2011.

"Would I play a part in the future monarch's upbringing? Of course I would," he said. "And it's another young baby growing up to play with, which I'd love to be a part of."

He also spoke about the time when Kate and Prince William broke up in 2007. Goldsmith told how Kate went to his villa in Ibiza - named Casa Bang Bang because of the music he plays - and how he helped to get the couple back together.

"Kate was very low. [She was] spending a huge amount of time on the phone, walking around the pool," he told the magazine.

"It's a very relaxing place and it has a very nice vibe and you can hear the sea at night. So in some small way I just hope that being there helped [Kate]."

Jokes with William

The Middleton family, along with Prince William, visited the villa in 2006. Even though Goldsmith was not there, he told how he made sure the future king enjoyed his stay.

"They all had the Ibiza experience - from mud baths to night club to learning how to mix music. Carole [Middleton] told me afterwards they had a brilliant time."

As a thank you, Carole Middleton, who is 10 years older than her brother, invited Goldsmith to their Buckinghamshire home to meet William.

"There was Kate in the kitchen cooking supper and William was making tea for everybody," Goldsmith said.

"When I saw them together you actually just thought, even if he wasn't going to be the king, they would make a great couple. They were very good together."

Goldsmith also compared Kate to her younger sister Pippa. "Kate works really hard at everything. She is brilliant at whatever she turns her hand to, but works at it, throwing herself into everything," he said. "Whereas with Pip, everything seems to come very easily."

St James's Palace has not commented on the interview.