As Gareth points out, Dickens modelled Fagin on a celebrated Jewish fence of the period, Ikey Solomon. However, there are good reasons to believe that Solomon was much more than just a Fagin.
In her book The First Fagin: the True Story of Ikey Solomon, Australian writer Judith Sackville O'Donnell shows Solomon to have been courageous and resourceful. She makes the bold claim that Ikey Solomon ought to be as recognisable an Australian as Ned Kelly or Phar Lap. OK - so you've probably heard of the bushranger Ned Kelly, but Phar Lap? Phar Lap was not a Cambodian revolutionary, but a famous racehorse. Hey, this is Australia.
To get back to the point - the subject of O'Donnell's book. He was known as 'The Great Ikey Solomon', not just because of his success as a London receiver - he was reputed to be worth £30,000 - but on account of his escape from Newgate Gaol to New York in 1827.
In America he learnt that his wife and four children had been transported to Van Diemen's Land. He at once took ship to join them, at the risk of discovery by the British authorities. But he was 'determined to brave all for the Sake of my dear Wife and Children - I don't care what may happen'. Just as Ikey is cruelly represented, there is no evidence that Ann Solomon was the harlot, shrew and brothel-keeper of the pamphlets of the time and Bryce Courtenay's The Potato Factory. She was largely a victim of injustice.
Dickens knew of Ikey Solomon, and there are strong similarities between Ikey's trial and Fagin's in Oliver Twist. But unlike Fagin, Ikey did not hang. He was to be jailed in Van Diemen's Land, now Tasmania - at Richmond and Port Arthur - and the family reunion would not be easy. For all that, Ikey's action was heroic, and the Solomons' legacy in Tasmania is one of substance rather than criminality. Drawing extensively on archival material and Ikey's letters, The First Fagin is a corrective to the harsh portrayal of Fagin and Ikey in fiction.