His name is Prince Rupert zu Loewenstein. He died two weeks ago. From his obituary in The Economist:

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.