His company, the Really Useful Group, is the dominant force in British theatreland, he owns a house in Knightsbridge and a 10,000-acre country estate in Berkshire which was the setting for Watership Down, a flat in New York and a villa in France. He owns two stud farms and a string of racehorses. In recent years, much of his fortune has been lavished on art, making him by far the most sought- after client of Bond Street dealers and major auction houses.
Nobody in Britain can match his collection of Victorian and Pre-Raphaelite paintings. In the world he now ranks among the top five private collectors.
It is not a passing fad. Sir Andrew has been buying art since he was a boy, when he developed a passion for church architecture and Burne-Jones's stained glass windows. Ultimately, his aim is to build an Andrew Lloyd Webber Museum, possibly on London's South Bank. Until then his collection is scattered among his homes or on loan to galleries around the world.
Two of the finest works he has been involved in buying do not, however, belong to him. In April 1992, after threatening to move abroad if Labour won the election, he formed The Andrew Lloyd Webber Art Foundation to save masterpieces, themselves threatened with going overseas, for the nation.
The foundation has three trustees: Sir Andrew, his wife Madeleine and Patrick McKenna, his long-time business associate. David Mason, the St James's dealer and spotter for Sir Andrew of works as they become available over the years, was appointed its adviser.
Registered at the Charities Commission as a charity, the foundation listed as its objects, "to advance the education of the public in the knowledge, understanding and appreciation of the arts generally and in particular in the field of painting".
Its other aims included the holding of lectures and seminars on the arts.
Its first foray into the art market was spectacular. Armed with a handsome donation from Sir Andrew, the foundation emerged as the pounds 10.1m buyer of Canaletto's 1749 painting of Old Horseguards from St James's Park.
Although by an Italian painter, the work, one of the finest depictions of London, was regarded as uniquely British. That sense was echoed by Sir Andrew, who said that he was delighted Britain's art lovers would have a chance to see it, on display at the Tate.
Sir Tim Bell, his spokesman, was quoted as saying: "The whole point of The Lloyd Webber Foundation is to secure treasures which will be seen by as many people as possible."
However, in a deal between the Charities Commission and the foundation, provision was made that, for part of the time at least, the work - and others the charity purchased - could hang in private on the walls of Sir Andrew's home. That rare concession was made, said the commission, because it was regarded as a better alternative than having the work languish in a bank vault for those periods when the Tate did not want it on exhibition.
The deal meant that, for pounds 3,892 paid to the charity, the multimillionaire was able, for five months in 1994-95, to enjoy gazing at a pounds 10m painting at his own home. It also meant that the Government, which covered the cost of the tax breaks to the charity, was subsidising the purchase, which for part of the time was used for his private pleasure.
This arrangement was repeated with other paintings the foundation owned. For most of the time they were on public view, but there were periods when he paid the charity a licence fee to enjoy them in private.
It is not known if the foundation's costliest purchase, Picasso's Blue Period portrait of Angel Fernandez de Soto, bought for pounds 18m at Sotheby's in New York, has also been on his walls. Accounts for the year covering the purchase have yet to be filed. All the National Gallery, where it was on display for six months this year, would say was that the Picasso had gone back to the foundation.
Sir Andrew's use of the paintings would appear to be contrary to the normal rules governing charities - that trustees are not supposed to derive any benefit from them. The Charities Commission said that an exception had been made in this case. Ideally, said a spokeswoman, the paintings would go to a museum or gallery for public exhibition. However, when the charity was set up, the point was made that it would be better during a period when no gallery required them if Sir Andrew had them at home. That was known, she emphasised, at the time the charity was registered.
Working on the same principle, and keen to see if the Independent on Sunday could share in the charity's treasures, by hanging the Canaletto on the wall of its editor's office - she has a blank spot which would take the sumptuous painting nicely and would provide a pleasant contrast to the drab modernity of Canary Wharf - we phoned Sir Andrew's office.
If it were during a period when it was not needed by a museum or gallery, and if we paid the same rate as Sir Andrew, could we also have the pounds 10m Canaletto for five months? We would happily pay the pounds 3,892 he paid. We would insure it and provide the necessary security.
Clare Campbell-Preston, his press adviser, was bemused. "I will have to talk to the right people," she said.
Shimon Cohen from Sir Andrew's office rang us. When the same request was put to him, he said: "I did not hear that correctly, tell me that again. You want to rent it?"
Regaining his composure, Mr Cohen raised the issue of security and insurance. "I do not think the art foundation lends out its paintings," he said, with an air of finality. But it did for Sir Andrew? "There may be an exception for one of the trustees," he said.
Later, Mr Cohen told us that hiring it would not be easy. A lot of paperwork would need to be completed. Asked how it was that a painting belonging to the charity ended up hidden from general public view, his spokesman said that "it was purchased so that it could be on public display but for some of the time it does hang at Sir Andrew's home".
Subsequently, Mr Mason sent a fax from his St James's gallery: "I have been advised by Sir Andrew Lloyd Webber's office that, on behalf of your editor, Ms Rosie Boycott, you have made a request to rent the View of Horseguards Parade by Canaletto that belongs to the foundation." Mr Mason asked that the request be put in writing. We complied. The editor's wall is still waiting.