A non-fiction thriller

Even if true, these allegations are unlikely to do much damage to Juan Carlos's reputation (which in any case is practically bullet-proof in his home country). This is partly because it's not the first time that such rumours have done the rounds.

Albert Sola died on October 8th last year, in the Catalan town of La Bisbal d'Empordà, where he worked as a waiter. Aged 66, he had claimed for decades to be the eldest child of Juan Carlos. Sola never produced any conclusive evidence for his claims though, and in 2015 Spain's supreme court rejected his paternity lawsuit against the emeritus king.

Belgian woman Ingrid Saurtiau had more luck, at least initially. In January 2015, the Supreme Court accepted her paternity suit against the former king, who she says had a brief affair with her mother (not also Sola's mother) in the mid-1960s. Two months later, though, it dismissed her case.

Then, as now, these claims weren't the worst thing to happen to Juan Carlos. Another type of scandal forced his abdication in 2014, when it emerged that the then-king had enjoyed a luxury elephant-hunting trip to Botswana as Spaniards endured a recession (although the fact that another of his alleged lovers, Danish businesswoman Corinna Larsen, was present on the holiday didn't do Juan Carlos any favours).

Eight years on, rumours about Alejandra and her aristocratic mother pale in comparison to what the new book's authors claim to reveal about Juan Carlos's offshore financial activities: according to the blurb, King Corp is a "political thriller [although non-fiction] about the financial empire of Juan Carlos I, through which Swiss lawyers, arms dealers, drug traffickers, spies and IBEX executives parade".

At first glance, King Corp doesn't appear to be the work of crackpot conspiracy theorists, but rather of two respected professionals whose research has involved "exclusive access to bank documents, emails, photographs and testimonies from bankers, businessmen, Zarzuela workers, the military, members of the secret services and ex-lovers of the former head of state".

If I were part of Juan Carlos's legal team, that's what would be keeping me up at night, not another allegation that Spain's adored ex-monarch sired a son or daughter via an extramarital affair.