That's the view of Grant MacDougall, who looks after football memorabilia for Christie's, the auction house. He says a programme from the 1966 World Cup final, signed by Sir Alf Ramsey and the full England squad, would now be worth between pounds 300 and pounds 500. Without signatures the programme would fetch just pounds 10 to pounds 20.
The autographs of the Manchester United players who died in the Munich air crash of 1958, the "Busby Babes", would fetch between pounds 200 and pounds 400.
Outside the world of sport, two of the most sought-after signatures are those of Winston Churchill and Marilyn Monroe. Last year Christie's sold some early love-letters written by Churchill for about pounds 20,000 each. A signed photograph of Monroe could be worth more than pounds l0,000.
Other "first division" names include the Beatles, Queen Victoria, James Dean, Theodore Roosevelt, WG Grace and Jimi Hendrix. Chris Kendall of Frasers, a specialist dealer in London, says British investors can still make money from this market, especially as prices here are far lower than those paid in the US.
"Ten years ago you could pick up a signed Beatles photograph for about pounds 50," he says. "Five years ago we were paying about pounds 150, and now a good- quality l0 by 8 is going to sell for at least pounds 1,500 - more probably pounds 2,000.
"Our typical customer is a professional in his thirties or forties who is buying a piece he can hang on the wall, which is a good talking point but also a sound investment."
The really valuable signatures are from historical figures or entertainers who remain very well known. Some more recent pop stars such as Madonna, Prince and Michael Jackson are starting to prove collectable, but these are a gamble. Giles Moon of Christie's popular entertainment department suggests a few brave souls might speculate on the signatures of Liam and Noel Gallagher of the rock group Oasis.
Mr Kendall says: "When people are looking for a portfolio for investment, what I would suggest is that 80 or 90 per cent of it is solid material. That is material you always know is definitely going to rise in value, although maybe only slowly. Then there's mid-range material - I would suggest artists' letters. Letters written by Monet, Renoir and the Impressionists are still very inexpensive."
Beatrice Boyle, who looks after the historical side of this business for Christie's, says: "The only politician who really fetches a lot of money is Winston Churchill. The rest of the prime ministers tend to be banded into one lot - they don't really fetch a lot by themselves, unless it's a letter saying something controversial. Context in letters is very important."
The Churchill love-letters may have fetched pounds 20,000 each, but a more routine letter may be worth only pounds 300. Signed photographs could be worth anything from pounds 300 to pounds 1,000, depending on the size of the print. The ultimate Churchill item, says Mr Kendall, would be a signed copy of his "We will fight them on the beaches" speech.
When it comes to entertainers, Marilyn Monroe is in a class of her own. This is partly because she often had assistants sign photographs for her, so genuine signatures are rare.
Mr Kendall says: "Demand for her worldwide is enormous, and good signed photographs are very, very hard to come by. You're going to have to pay over pounds 10,000 for one of those. Having said that, we sell things like a personal cheque, framed and mounted with a portrait, for about pounds 4,000."
Last year a pair of publicity stills for the film Gentlemen Prefer Blondes, showing Marilyn Monroe and Jane Russell, was sold at Sotheby's for pounds 7,360 thanks to Monroe's signature on the prints. The guide price was just pounds 1,500 to pounds 2,000.
As with Monroe, signatures of US presidents may turn out to be less than genuine as they often used an "autopen" - a machine for busy people that produces copy signatures which are almost worthless.
Surprisingly, Elvis Presley features much further down the list for valuable autographs. Christie's Mr Moon says: "Presley is collectable, but he's not in quite the same league as the Beatles. There seem to be more examples of his signature, which probably holds the price down a bit. His autograph on a piece of paper would probably make pounds 150 to pounds 200. It's better if it's from his army days. He signed a lot of publicity posters and postcards and that sort of thing while he was in Germany."
Autographs find their way to the auction houses from private collections or, in the case of some of the grander historical names, from a visitors' book which has been in a family for many years. Ms Boyle says: "Autograph hunting has been standard practice for hundreds of years - it's certainly something the Victorians did."
If you think you may have some signatures worth selling, the first step is to take them to an auction house and get them valued. Ms Boyle says: "There might be signatures in there you can't recognise. Auction houses, because they see so many of them, do start to recognise people's handwriting. Stalin's signature, for example, doesn't look anything like 'Stalin'."
o Contacts: Frasers 0171 836 9325; Christie's 0171 581 7611.