THE music of the Rolling Stones did nothing for Prince Rupert zu Loewenstein. Perhaps “Paint it Black” was not too bad. Otherwise, he doubted that their cacophanies counted as music at all. If you made your way backstage at a Stones concert, passing through dozens of grades of status and access, past aides in black T-shirts and girls in not much, you would find him at the very nerve-centre, a portly, kindly figure in immaculate suit and tie, with his hands clapped over his ears.

He was there, on every tour for 39 years, because his financial nous had turned the Stones into the most lucrative rock band in the world. Mick had his hip-swivelling energy, and Keith his wild guitar; Prince Rupert, behind the scenes, contributed wisdom and suavity to the cafetière, along with high-class fun. Before he arrived, in 1969, they were stuck in a recording contract with Decca and tied to a financial adviser, Allen Klein, who creamed off half of what they earned. Over years of litigation Prince Rupert liberated them, restoring their rights to regular revenue from their songs. He also built up a global touring machine that pulled in millions from merchandising and corporate sponsors: Budweiser, Volkswagen, Chase Manhattan. Thanks to him, the Stones in 2006 paid tax at 1.6% on 20-year earnings of £242m.

Nonetheless, to stumble upon him backstage was as odd as to come across Jumpin’ Jack Flash in the pages of the “Almanach de Gotha”. He was the son of Bavarian aristocrats, and properly speaking (as he always spoke) was called Loewenstein-Wertheim-Freudenberg. He could trace his descent on his father’s side from the royal house of Wittelsbach; his mother, the Countess of Treuberg, was related to the kings of Brazil. From a somewhat solitary childhood, which included being abandoned in Grasse when he was six with only a maid and a cook, he recalled his father telling stories of his ancestry and stressing the importance of tenue—the bearing necessary to a gentleman.

Not that there was much left. The beautiful Schloss near Munich and the 5,000-hectare estate had been sold to pay racing debts. Estate factors (much like the Stones’ previous advisers) had siphoned off the revenues. Neither of his parents could cope with things financial at all. As a child, he would be parked by the Ritz bar while his mother begged for loans from the manager of Barclay’s, next door. Yet, curiously, he seemed to have “an instinctive sense of money” himself. So in 1962 he and some friends bought Leopold Joseph and Co, a small merchant bank, and expanded its client list by holding dinners and parties at his house in Holland Park.

The suggestion that he might help the Stones came from Christopher Gibbs, an art dealer he had met dans le monde. (The idea of steering them towards Atlantic Records arose when he met Ahmet Ertegun at a dinner given by Hardy Amies.) He did not know who the Stones were at first, and had to ask his wife, who read the popular newspapers. He found then that he had already met Mick, tripping over him as he lay stoned on the floor at a party in Chelsea. At a second meeting, they bonded at once. He discovered that Mick was bright, honest and business-minded, and Keith deeper than he appeared. As a man used to “tremendous transience”, a European cosmopolite with four languages, he warmed to these travelling players; and they to him, because he could open gilded doors.

To sort out the “rats’ nest” of their financial affairs required not only severing the Klein connection, but temporary exile from Britain to escape swingeing taxes. Prince Rupert, though tempted by the Caribbean, sent them to the south of France. He could not bill them for three years, because they had no money, and other financial firms (considering him a rara avis anyway) scorned him for mingling with long-haired layabouts. By 2007, just before their ways parted, he was advising the chief layabout on how to invest £40m in stocks.

Financial rescue was not all he managed for the Stones. He advised them when they split from their various wives and girlfriends, and chided them for their tomfoolery during discussions over contracts. He interjected a mood of calm consideration where necessary, “the rock ‘n’ roll equivalent of one of Aristotle’s walks through...the Lyceum”. The last advice he gave them was to sell off the band’s assets for a huge sum and then retire from performing. This advice they did not take.

Saucy, not satanic

He might have moralised as well, for he was an ardent Catholic, holding high office in the Constantinian Military Order of St George and the Knights of Malta. In fact, he raised only one objection to the Stones’ cavorting, asking them not to feature tumbling crucifixes in a video on the “Sympathy for the Devil” tour. Apart from that, he found them “saucy” rather than satanic. What happened in their dressing rooms was their own affair. Whatever substances they ingested were up to them—unless they risked prison for it, as Keith did. He worried far more that Mick had a habit of turning up late for dinner.

As for the red-tongue logo, he thought it excellent. It might be repellent, but it gave the band a global brand. And the same could be said, he supposed, for the music; though he would rather have Bach any day, or an evening at the Wigmore Hall.