On the face of things, it looks like a happy family snap.
King Juan Carlos of Spain sits with the small Prince William, while a radiant Princess Diana, a protective arm round toddler Prince Harry, leans in to share a pleasantry with the good-looking monarch.
But look again. At the other end of the couch, Prince Charles seems scarcely part of the same holiday party in 1986. He is staring glumly straight ahead like the proverbial gooseberry.
Princess Diana is rumoured to be just one of the many young ladies the king, now 74, pursued in a romantic career in which — like his namesake, the seducer Don Juan — he is said to have bedded more than 1,500 women.
Distant: Prince Charles stares into the distance in this 1986 photograph showing him, Diana and the young Princes William and Harry with Queen Sofia and King Carlos of Spain
The explosive claim is made in a new book by Barcelona-based author Pilar Eyre, who has already written six volumes about the Spanish royal family.
Imperious and suave, Juan Carlos looks every inch the old-style monarch . . . with the autocratic manners to go with it. He loves hunting bears, skiing and boating — and bedding the opposite sex.
Apparently, it is an open secret in his circles that he is such a keen womaniser that the only woman he does not spend much time with is his wife, Greek-born Queen Sofia. According to Eyre, the two have not shared a bed for 35 years.
In fact, the book says, following an operation on a benign lung tumour at a Barcelona hospital in 2010, the woman who spent most of the time consoling him during his convalescence was a 25-year-old German interpreter called Corinne.
Another shot of the princess during the 1986 holiday. She allegedly told her bodyguard that the king fancied her
But can it really be true that our very own Princess Diana was one of Juan Carlos’s most significant conquests? And that it was the relationship between her and the then 48-year-old king, in the prime of his romantic life, that finally put paid to any chance of reviving his marriage?
It is certainly the case that the Princess, together with Prince Charles and their young children, holidayed in Majorca with the Spanish royal family several times during the Eighties.
Charles never felt at ease on the sunshine island and much preferred visiting the Duke of Wellington’s estate near Granada on the mainland where the shooting was good.
But Diana, who loved lounging about on yachts in stylish bathing suits, was right at home on the shores of the Mediterranean where she could show off her figure. And the king, who appreciated displays of female beauty, seems to have acted on an impulse to get closer to her.
After her first trip to Majorca in 1986, Eyre alleges Diana told her bodyguard Ken Wharfe that Juan Carlos fancied her. Apparently, the king made all sorts of excuses to get tactile with her and used to love bending down with her and inviting her to stroke his old German shepherd dog, Archie.
Another royal biographer, Lady Colin Campbell, has long insisted that the Princess and the king embarked on an affair while on a cruise with their spouses in August 1986, and that they took up with each other again the following summer.
‘Diana did it to make Charles jealous, but it didn’t work,’ says Lady Colin. ‘Charles couldn’t have cared less.’
According to Eyre, rumours of the affair intensified later over the curious case of some photos of Diana in a state of undress. These were touted around the world’s publications, only to be taken off the market when someone in Spain paid $45,000 (£29,000) for them. That someone is rumoured to have been Juan Carlos, who wanted to protect the Princess’s reputation.
But why rake all this up now? Diana is long since dead, while Juan Carlos, though he retains an eye for a pretty woman, has made it quite plain that he would never divorce his wife, with whom he has three children and eight grandchildren.
Eyre says she has revealed it for Queen Sofia’s sake. ‘In a macho country like Spain, the king’s womanising image makes him very popular,’ she says. ‘Even the women don’t reproach him. On the contrary, they love him because he has such a seductive manner with them. But they don’t feel the same about poor Queen Sofia.
Loveable rogue: Barcelona-based author Pilar Eyre claims that in macho Spain, the King's womanising makes him very popular
‘She is seen as a cold, aloof foreigner. I wanted to show what she has had to put up with.’
Eyre says she tried hard to find out whether the Queen might also have had lovers in her time, but could come up with nothing. Though as a young woman she had caught the eye of the Duke of Kent — first cousin to our Queen — the Duke then fell in love with the Englishwoman he married, Kathleen Worsley.
Sofia dutifully entered into an arranged marriage in 1962, having met the highly eligible Juan Carlos on a cruise specially convened to introduce Europe’s young royals to each other.
By 1968, they had produced two daughters and Crown Prince Felipe. But though Sofia had fallen deeply in love with her husband, Eyre says Juan Carlos was still playing the field.
And by 1975, when he finally came to the Spanish throne after the death of the dictator General Franco, the new Queen was nursing a great sadness. For by then the royal couple were more or less estranged as a result of the king’s persistent womanising.
According to the book, one of Sofia’s greatest humiliations happened a couple of months after Juan Carlos became king. All of a sudden he sent for a new barber and underwent such a transformation Sofia was convinced he was sprucing himself up for a lover.
Notorious womaniser: The king is rumoured not to have shared a bed with his wife for 35 years
A few days later he packed his suitcase and said he was going hunting near Toledo. ‘It’s an all-male outing; you’d be bored,’ he told his wife. Unwisely, she decided to surprise him by arriving at the estate in the middle of the night with their children, the eldest of whom was 12.
She burst through the door, brushed past the servants and, taking the stairs two at a time, discovered her husband in flagrante with an unknown woman. But even being caught by his entire family did not encourage the king to mend his ways.
Eyre says that throughout her reign, Sofia has consequently been forced to content herself with a life of duty in Madrid, leavened by shopping trips with her daughters and occasional visits to England to visit her brother Constantine, the ex-King of Greece, who has lived in London since he was booted off the throne in 1973.
Lately she has taken solace in religion. She goes to Roman Catholic Mass every Sunday in the palace and attends Madrid’s Greek Orthodox church as well. Her devotions seem to annoy Juan Carlos even more.
The king raised his voice to his mother-in-law, Queen Federica of Greece, when he heard her telling her daughter how the Virgin Mary had appeared before her in a vision in a church near Madrid.
‘There was an intense light and peace!’ said Federica, at which point the king shouted: ‘Shut up, you! Don’t fill her head with this nonsense, she will believe it all.’
The tragedy is that despite his behaviour, the Queen appears to be as captivated by her husband as she was when they married 40 years ago.
At a recent family funeral she was seen holding tight to him and sobbing on his shoulder as if they were still the closest of companions.
Whether the book will rehabilitate Sofia in the eyes of the Spaniards or merely add to the prestige of Juan Carlos remains to be seen.