Fergie claims she and Diana were arrested for 'impersonating police officers'

Sarah Ferguson has recalled an incident involving the late Princess Diana, some smoky bacon crisps and the back of a police van.

The former Duchess of York has been on a major media blitz to promote her new Mills & Boon romantic novel.

As the ex-wife of Prince Andrew, she has a healthy back-catalogue of royal stories to dip into whenever she pleases, and on Tuesday she described the unusual incident that took place on the night of her hen-do.

According to Fergie, she and Diana were dressed up as police officers and visited a night club, believed to have been near Buckingham Palace, to celebrate.

Watch: Princess Diana and Duchess Sarah Ferguson 'got arrested for impersonating police'

Speaking on the Kelly Clarkson Show in the US, Ferguson explained: "I was just still Fergie - I wasn't married yet - and we went into this nightclub. We sat down and the waiter came up to us and said: 'Excuse me, this is a member's club and it's for fun and we don't serve police officers here' looking straight at us."

Fergie told host Kelly Clarkson the pair were then kicked out of the club and, as they left, the Princess of Wales spotted a passer-by.

"A lady was getting out of the cab and Diana said 'She's got my dress on!' I said 'Dutch, no, you can't say that - we're meant to be police officers'."

Fergie continued that the two were then arrested by the Parks Police, who are responsible for policing some of the parks in central London, for impersonating officers.

"We got in the back of the van, she had put her engagement ring round the other way and I put mine round the other and we're sitting there like this and she just looked round and saw smoky bacon flavoured crisps and started taking them and eating them.

"The policeman in the front said 'You can't do that!' Then eventually they realised that it was Diana and me."

Ferguson married Prince Andrew in 1986 after being set-up with Andrew by Diana, with whom she enjoyed a close but at times tumultuous friendship.

They had known each other since childhood — both as fourth cousins and through their mothers who had in turn been friends since they were teenagers.

Once they were both married into the Royal Family, they were relentlessly contrasted in the press and eventually had a falling out in the year before Diana's death.

"The saddest thing, at the end, we hadn't spoken for a year," Sarah has previously told Harper's Bazaar. "Though I never knew the reason, except that once Diana got something in her head...I tried, wrote letters, thinking whatever happened didn't matter, let's sort it out. And I knew she'd come back.

"In fact, the day before she died she rang a friend of mine and said, 'Where's Red? I want to talk to her."

Watch: The bitter story behind Diana's 'revenge dress'