Ex-EastEnder turned politician Michael Cashman has said that he and his gay partner slept in Prince Philip's bedroom at the Queen's official residence in Northern Ireland.
He said he and his late lover Paul Cottingham had a number of visits to Hillsborough Castle at the invitation of his friend and former Secretary of State Mo Mowlam, who he said "loved to throw a party".
In his new memoirs the former actor, best known for his role as Albert Square's Colin Russell, said there were regular boozy bashes held by Mo but that he was initially knocked back from staying in the Queen's quarters.
But he also revealed another queen did make it to the chamber - drag queen Lily Savage, aka Paul O'Grady, who ignored protocol and kipped in Her Majesty's bed.
Michael (69) said: "Mo Mowlam loved to throw a party! Trying to keep the feuding political parties of Northern Ireland together was difficult to say the least, so during weekends when she was at the secretary of state's official country residence, Hillsborough Castle, Paul and I were often invited.
"Our first visit to Hillsborough was with Anji Hunter, Tony Blair's trusted advisor, and her family, Jackie Ashley and her partner Andrew Marr, and the actor Richard Wilson.
"We arrived on the Friday ahead of the rest of the party. David, the butler, said, 'The secretary of state has told us to make you comfortable. You are to choose your bedroom and she should be here by supper.'
"He then whisked us around the palatial building, set in beautiful landscaped grounds, and showed us the options for accommodation.
"First we inspected the Queen's bedroom, with its grand double bed, then Prince Philip's bedroom, which adjoined the sovereign's, both of which had separate bathrooms. Finally we were shown a couple of smaller royal bedrooms.
"It seemed the lower down the royal pecking order you went, the smaller the bed and the less luxurious the bathroom. 'And have you chosen a bedroom?' asked David. 'Well, the Queen's bedroom...'
"There was just the faintest shake of his head. 'Prince Philip's has lovely twin beds,' he said. 'He put you where?' asked Mo when she arrived. 'Philip's.' 'F** me. If ever there were two men who should be in the Queen's bedroom, it's you two. Okay. Next time.'"
Michael, who went on to form gay rights group Stonewall and become a Labour MEP, is now a member of the House of Lords and said he enjoyed "a raucous" night with his partner Paul and Mo with her husband, Jon.
He said Hillsborough butler David also told him how "he had once needed to remove a number of silver ashtrays and spoons from the pockets of a Commonwealth high commissioner".
Michael detailed another party that Mo held after a BBC telly show celebrating Northern Ireland that as well as himself, included Patrick Kielty, Eamonn Holmes, Lily Savage and former EastEnders co-star Michelle Collins.
He said: "The artists named and celebrated people in the audience who had 'made a difference' to their communities, and the show felt like a success. At the reception afterwards in the adjoining Europa Hotel, Mo was mobbed by people from both sides of the sectarian divide. The outpouring of love was unbelievable to witness.
"After 40 minutes she still hadn't reached the front door of the ballroom. She dispatched Paul to get her a Bushmills whiskey and slowly made her way towards it.
"When she left some time later, she said 'Cottingham, get some stars to come back, some fun people. I need to party.' And he was as good as his word. With the party at the castle in full swing, I convinced Mo to stay up a little longer on the promise that I would wake her in the morning.
"A little longer turned into a lot and the next morning I woke abruptly to the alarm and a memory of Lily Savage/O'Grady carrying me to my room. Quickly I pulled on a shirt over my pants and stumbled to the secretary of state's bedroom to wake her.
"As I came out a minute later, unsuitably undressed, I came face-to-face with an armed RUC man patrolling the corridors. 'Good morning,' I said. 'Good morning, sir,' came a stern reply. A week later Mo said she had heard the gossip that she was 'now sleeping with gay men'. Mo left for work while I sensibly went back to Paul for what I hoped would be a quiet morning in bed.
"But before I could drift off there was a loud banging at the door. 'Mr Cashman! Mr Cashman! There's someone sleeping in the Queen's bed!' I remembered. 'Savage!'
"Mo loved it all. There was nothing shocking or unacceptable when it came to letting your hair down and living. We took her to see the Rocky Horror Show at the Belfast Grand Opera House and she invited the entire cast, including Jason Donovan and Nicholas Parsons, back to the castle for the night.
"The party of all parties ensued. We sang, danced and drank until daylight. The comments her visitors recorded in Hillsborough's official guestbook - which included entries from Diana, Charles, the Queen and others - were so lurid that Mo ordered for the book to quietly 'disappear'.
"She later told me that some of her Special Branch officers thought that in going to see Rocky - she had taken them with her - she had scraped the very bottom of the barrel."
In his new book, One of Them: From Albert Square to Parliament Square, Michael also said Mo was devastated to be replaced by Peter Mandelson as secretary of state and told him she had been "f***ed over".
He said: "She was angry, confused and hurt. After years of impeccable service and devotion to the cause of peace in Northern Ireland - built up from those unseen years of work in opposition - they had, in her words, 'f***ed her over'. When I said that it was unfair she merely replied: 'It's nothing to do with fair. The party always will.' It was a political fact of life for her, but she felt betrayed. Mo and Jon moved to Hackney and the glamour-seekers started to slowly fade away.
"Dawn French was always there for her, however: she never forgot the weekend in Hillsborough when she and Lenny Henry were going through a rough patch. The tabloids traced them to the pub along the road from the castle.
"Mo took control and had her bulletproof car backed up to the pub's exit so that Lenny and Dawn could slip away, unnoticed and not photographed."
Elsewhere in his book Michael also said his first visit here was with a former lover of two years called Andrew, who was a young director, during the Troubles and he insisted on sneaking into Divis Flats. He said: "He took me to his hometown in Northern Ireland, where his parents still lived, and showed me the divisions of communities and people.
"The country was being torn apart by the Troubles then, by sectarian violence and bombings. In the late Sixties, the British Army had been brought in to restore order.
"By the late Seventies there seemed no end in sight. There were no-go areas for Catholics, and for Protestants - or even people who were suspected of being either.
"Against his protests about his safety and mine I insisted on him sneaking me into the renowned republican Divis Flats in West Belfast and then onto the nearby Falls Road.
"A man came out of a second-hand furniture shop and stared at me. A young child was dispatched on his bike to ask my name, where was I from, and why was I there.
"Andrew, emphasising his Northern Irish Catholic accent, answered for me. As the boy cycled back to the waiting man we made a fast exit."
One of Them: From Albert Square to Parliament Square is on sale now.