The finances of the Queen's official composer are at the centre of a fraud investigation after the discovery of an alleged £500,000 "black hole" in his accounts.
Sir Peter Maxwell Davies, Master of the Queen's Music, whose social circle includes Elton, is one of Britain's most influential and respected musicians.
Last week, Michael Arnold - his friend and long-serving manager - was arrested after Sir Peter, 72, found sizeable discrepancies in his business dealings.
Mr Arnold, who has looked after the composer's financial affairs for more than 25 years, was later released on police bail. He has not been charged.
Sir Peter, who has conducted some of the world's finest orchestras, including the BBC Philharmonic and Royal Philharmonic, refused to discuss the on-going police investigation.
But friends said he has been deeply disturbed by the alleged fraud, thought to involve his private company Maxopus, one of the Internet's first classical music download websites.
Sir Peter set up the service with Mr Arnold and his wife Judy in 1999 and Mr and Mrs Arnold were appointed directors in 2000. Sir Peter has dedicated pieces of music to the couple.
The composer, who lives on the remote Orkney island of Sanday, contacted the Northern Constabulary in Inverness after becoming suspicious about proceeds he should have received from his work.
After initial inquiries were made in Scotland, the investigation was passed to the Metropolitan Police. An officer from Northern Constabulary has also travelled to London to assist in the operation.
Mr Arnold, 73, was arrested by the Met's Kensington branch on April 18 and has been bailed to return to Notting Hill police station later this month.
On Friday, Mrs Arnold refused to discuss the investigation at the Fifties home she and her husband share near Earl's Court underground station in West London.