Even people with no interest at all in art have probably heard of Francis Bacon, for whose work a collector has just paid a record £7.9m in New York. But even Bacon fans are unlikely to know of Reg Butler, a friend of Bacon's who exhibited with him and was at one stage more successful. So what happened to Butler that means his work can now be bought for a fraction of the price a Bacon?
"It's a combination of reasons," says James Rawlin, head of 20th century British art at auction house Sotheby's. "Bacon was a self-publicist, but Butler was quiet and relatively self effacing. Despite the fact he was probably the best known of the younger generation sculptors we had by the end of the 1950s, and was exhibiting all over the world, somehow we have let his reputation slip.
"The international reputation of British artists in the 1950s and 1960s was no less potent than the international reputations of artists now but I think sometimes we don't tend to look at our pictures and sculptures as internationally as we might."
Butler isn't the only British artist to be caught in this rut. Terry Frost died a few years ago and there is work of his from the 1940s up until his death. His real period of achievement was the early 1950s and 1960s, then he was exhibiting all over the world.
Recently, a small, but beautiful picture from that earlier era came up at auction and set a new record. Since November 2004 the record price for a Frost has gone up around six times, from £20,000 to £100,000.
Modern British art has always been dominated by artists linked with the St Ives movement, but there was a group which came under the umbrella of the Constructivists who were working in London at the same time. Collectors are starting to look more seriously at these artists, who include Adrian Heath, Kenneth Martin and Victor Pasmore, who have always been known about but rather forgotten.
Sotheby's had a Heath piece in its last sale, one of his most important to have come up in the past 10 years. It made £105,000. This sounds pricey, but if you wanted to buy such a major work by a defining French figure from that period you would be paying four or five times that, and for an American, even more.
The two best known figures associated with the Independent group are Sir Eduardo Paolozzi and William Turnbull. The scarcity of good Paolozzi works means that the first major piece that appears is going to be well contested.
So how does the market rehabilitate formerly popular artists? "Usually when we see a lift in interest in either a period or a group of artists it's often a mix of things," explains Rawlin. "Within a three- or four-year period you'll usually see in no particular order, perhaps a good museum show or sometimes the publication of a book.
"Sometimes it's a dealer exhibition when a nice catalogue is produced, or it's a work in the salerooms. When we manage to persuade a collector with a great piece to sell it, and it does really well, then that can break through the deadlock."
The difficulty for auctioneers is that if you have a piece by a not-so well-known artist there can a vicious circle, because you don't want to sell it as you think it won't make much. As a result, nothing comes onto the market to stimulate interest. "Still, this is a sector that is growing and expanding and prices are going up," says Rawlin.
The first book on Reg Butler has just been published, and it will be interesting to see what effect that has on his reputation. There was a Terry Frost work in the last Sotheby's sale that raised £159,200, way above its esitmate. Two years ago the price would have been more like £20,000 to £30,000, which shows how collectors who don't just look at the big names, but also their contemporaries, can be making some very good investments.