A chalk sketch of a naked Adam by Michelangelo - bought by the British Museum for £600 in 1926 but now worth an estimated £15m - is today proclaimed the nation's best-value art buy of all time.
The study for the vault of the Sistine Chapel is one of several masterpieces whose market prices have multiplied since they were saved for the nation, according to the National Art Collections Fund, Britain's leading art charity.
But for every undisputed "bargain" snatched from the jaws of private investors by forward-thinking galleries and museums, there has been a tragically misguided purchase whose value has plummeted since its original sale.
A painting credited to Giorgione and bought by the National Gallery with the Art Fund's help for the equivalent of £566,000 has since been valued at a fraction of its original price after being re-attributed to a lesser artist. Similarly, an elaborate Bronze Age torque sold to Ulster Museum for £5,000 in 1968 is judged to be almost worthless, having recently been exposed as a 20th-century fake.
The Art Fund has compiled its list of "best and worst art buys" to coincide with its centenary celebrations, which will be marked with an exhibition at London's Hayward Gallery, sponsored by The Independent on Sunday.
The charity hopes the list will encourage institutions to buy more high-quality items by emerging artists at an early stage, in anticipation of their prices rising as and when they become famous. It wants galleries to collaborate more, to give them a better chance of saving works for the nation.
However, the Art Fund's call to arms comes with a warning. In recognition of its own past errors, it aims to discourage galleries from impetuous purchases on the basis of questionable advice about the prospects of promising artists. Such folly has been blamed for the decision by galleries in the early 20th century to snap up paintings by the all-but-forgotten Alfred Stevens, instead of paying similar sums for works by masters such as Monet.
Not everyone feels that the charity's candid advice goes far enough. The veteran critic Brian Sewell called on it to warn public galleries against "wasting" their scarce resources on "worthless" Brit Art works by the likes of Damien Hirst and Julian Opie.
The Art Fund has illustrated its "dos and don'ts" of art-buying using a series of examples of past purchases that it helped to finance. Of the Michelangelo drawing, Study for the Creation of Adam, which was bought for £600 (equivalent to £21,836 today) 77 years ago, it says: "At £600, this Michelangelo, which is probably one of the most famous studies in the history of art, looks like an absolute bargain. It would probably fetch up to £15m if it came up for sale today."
Similarly,The Toilet of Venus by Velazquez - better known as "the Rokeby Venus" - was presented as a gift to the National Gallery by the Art Fund in 1906. The painting, bought for £45,000 (£3.13m in today's money) is now "conservatively valued" at £70m.
Among the most embarrassing of the "worst buys" is a supposedly Bronze Age neck torque purchased by Ulster Museum for £5,000 (£53,300 today) in 1968 with the help of a generous £1,000 Arts Fund grant. It was later debunked as a fake.
However, the charity is keen to trumpet its achievements. Its director, David Barrie, said: "Given that more than half a million objects have been acquired with our help over the last 100 years, it would be a miracle if a few misattributions or downright fakes had not crept in. If museums and galleries always played safe, then some wonderful opportunities would be lost."
Mr Sewell is unconvinced. "You can put a value on something when there is a standard market for it, but with something like The Toilet of Venus there has only ever been one," he said. "How do you put a price on something that can never be equalled?"
Rounding on the Art Fund for supporting acquisitions of works by Young British Artists, he said: "Everything they bought which has been made since 1970 is a waste of money."
'Saved! 100 Years of the National Art Collections Fund' will run at the Hayward Gallery from 23 October to 18 January
The best: Michelangelo's 'Studies of a reclining male nude'
What is it: Adam in the fresco 'The Creation of Man' (1508-12).
What they paid: Bought outright by the National Art Collections Fund for £600 in 1926 (£22,000 at today's prices) and presented to the British Museum.
Why it was a good buy: Widely admired at the time, it is now viewed as one of the finest studies in the history of art.
What it's worth: Would fetch about £15m if it came up for sale today.
The worst: Giorgione's 'Tebaldeo'
What is it: Giorgione's 'Scenes from an Eclogue of Tebaldeo' (circa 1505).
What they paid: Art Fund grant of £2,000 (£81,000) towards £14,000 (£565,000) purchase by the National Gallery in 1937.
Why it went wrong: Turned out to be by a little-known Italian named Fernando Previtali.
What it's worth: Previtali's work sells for as little as £80.Chapman brothers hit out at Tate
The Turner Prize-nominated artists Jake and Dinos Chapman have angrily attacked Tate Liverpool for dropping a retrospective of their work.
Art world insiders say the gallery decided to shelve next month's exhibition because of fears it would be eclipsed by a rival show being staged in London by Charles Saatchi.
And it would have been impossible to mount a Tate retrospective without Mr Saatchi's co-operation. As the Chapman brothers' biggest patron, he owns the bulk of their most celebrated works.
The director of Tate Liverpool, Christophe Grunenberg, said he decided a year ago to postpone the show after realising the dates conflicted with the Saatchi exhibition. He then put it off indefinitely, fearing the artists' Turner nomination and success at the Royal Academy Summer Exhibition would make another exhibition seem like "overkill".
The Chapmans reacted angrily to the news. "We are not that interested in just having a huge rambling retrospective show going around the country anyway," said Dinos Chapman. "We would have tried to do something different for the Tate, so if the argument is that there's a Chapman 'overkill' it wouldn't be, because we would've made new work for it."Reuse content