He was the prince who helped make the Rolling Stones as rich as kings.
Prince Rupert Loewenstein, the band's former business manager, helped the Stones churn their musical talent into mountains of gold. He died on Tuesday at age 80 after suffering from Parkinson's disease.
The Oxford-educated German aristocrat advised the Stones for almost four decades beginning in 1968.
He was introduced to Mick Jagger by a mutual friend at a time when the Stones were eager to extricate themselves from American manager Allen Klein.
"Rupert was a merchant banker, very pukka, trustworthy," Keith Richards said in his autobiography Life - and he proved invaluable to the band.
Loewenstein saw the Stones through their labyrinthine legal dispute with Klein, masterminded their year of tax exile in the south of France in the 1970s and oversaw their transformation from a rackety rock group to a formidable money-making machine that pioneered the lucrative mega-tour with the Steel Wheels extravaganza in 1989.
Born in Majorca in 1933, Loewenstein was a member of the Bavarian royal house of Wittelsbach. He studied medieval history at Oxford University before becoming a stockbroker and banker. Friend Hugo Vickers said that despite their different backgrounds, Loewenstein and Jagger "absolutely clicked," and the prince became closely involved in the band members' lives.
Loewenstein advised Jagger during his divorce from first wife Bianca and was godfather to the singer's son, James.
But Loewenstein always insisted he did not like rock 'n' roll. He said that distance let him view the band's affairs "calmly, dispassionately - though never without affection".
Loewenstein worked with the band until 2007 and last year published a memoir, A Prince Among Stones. Jagger was not amused, telling a newspaper: "I don't think your ex-bank manager should be discussing your financial dealings and personal information in public."
Vickers remembered Loewenstein as "a tremendous bon viveur" who threw grand balls and parties at his home in the wealthy London suburb of Richmond.
Loewenstein is survived by his wife, Josephine, two sons and a daughter.