Study for the Head and Hand of an Apostle was bought on the telephone for pounds 5,281,500 by an anonymous private collector, a world record for an Old Master drawing.
It had also set a world record for an Old Master drawing 12 years ago, when it was sold by the Duke of Devonshire for pounds 3.5m. A spokeswoman for the auctioneers, Christie's, in London, said it was a magnificent price for a magnificent drawing.
It was so valuable that experts refused to make public their estimate of the likely sale price, and they continued to refuse to do so after the sale.
The study is an auxiliary cartoon of St John the Evangelist, which was later transformed by Raphael in The Transfiguration, the outstanding masterpiece of his later years left unfinished by his death in 1520.