The Queen was once caught in bed with a "naked" Prince Philip by an embarrassed member of staff, a royal biography claims.
Her Majesty and the Duke of Edinburgh were walked in on at Clarence House in the early years of their marriage, according to ‘Young Prince Philip : His Turbulent Early Life’.
The royal couple spent many happy hours together in private but were supposedly interrupted on one occasion, Philip Eade suggests in the 2011 book.
"Philip had his own bedroom next door to Elizabeth's, an arrangement common to a great many upper-class couples at that time," Mr Eade wrote.
A door was reportedly built in between the wall separating the two bedrooms, reports the Daily Star.
Mr Eade continued: "The dressing tables in each of their rooms were placed close enough to the communicating door to enable them to talk to each other while dressing."
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Historian Robert Lacey told the author that the royal couple did "enjoy the visitation rituals which that system involves."
Philip's valet John Dean described this period as the couple's "happiest time".
The couple enjoyed many hours together and used to joke through the door, according to reports.
Mr Eade was told by another valet James Macdonald that he went into Philip's room one morning and saw the princess "in her husband's bed".
The biographer said: "While she was wearing her usual silk nightgown, Prince Philip appeared to be naked."
It has been reported that Philip regularly refused to wear pyjamas.
The Queen's Platinum Jubilee celebrations entered a third day on Saturday with the nation enjoying a four-day weekend.
Her Majesty scaled back on her appearances after dropping out of the official salute at the Trooping of the Colour parade and Friday's Thanksgiving ceremony at St Paul's Cathedral.
The monarch would usually salute her personal troops, the Household Division, on Horse Guards Parade.
But instead it was decided that Prince Charles, Prince William and princess Anne would make the salute this year.
Jubilee highlights on Saturday will include the Derby at Epsom Downs and the BBC's Platinum Party at Buckingham Palace.
The Queen had been expected to attend the Epsom Derby which is one of her firm favourites and one of England's racing highlights.
Her Majesty was to be greeted on the course with a special guard of honour including 40 of her past and present jockeys.
But she recently had to pull out of the event and will instead watch it on TV from Windsor, Buckingham Palace said.
Princess Anne expected to represent the family on her behalf.
It is only be the third time in her reign that she has missed the race, as the 96-year-old monarch looks to pace herself for the weekend’s celebrations.
At 8pm, the most star-studded event of the bank holiday weekend begins at Buckingham Palace.
An open aired concert will be headlined by Diana Ross and feature stars of stage, screen and sport including Sir David Attenborough, Emma Raducanu, David Beckham, and Dame Julie Andrews.
Also performing on the show's three stages will be Queen and Adam Lambert, Alicia Keys, Hans Zimmer, Ella Eyre, Craig David and George Ezra.
Duran Duran, Andrea Bocelli, Mimi Webb, Sam Ryder and Diversity will also feature along with a specially recorded performance from Sir Elton John.
The stages will be linked together by 70 illuminated columns, representing Her Majesty’s 70-year reign.
Her Majesty is not expected to attend, but will watch on TV instead from Windsor Castle.
