Heard the one about the Titian that turned into Mussolini?: A new code of practice has been introduced to crack down on 'shady' antique dealers. Dalya Alberge reports

STORIES abound of the con-tricks that antique dealers operating on the wrong side of the law have pulled off. You almost want to believe the one about an American who set his heart on a painting by Titian and found one in Italy, only to be told by the dealer that as part of the nation's heritage it was impossible to export.

However, the dealer could 'have a portrait of Mussolini painted over it, and when you get to America take it to your restorer, who will remove it'. Everything went to plan until the collector got a call from his restorer. The solvents had removed not only Il Duce, but the Titian. And underneath was a portrait of Mussolini.

According to one source, it is relatively common for dealers to have signatures painted on to Old Master paintings or details such as figures added to otherwise dull landscapes. Sometimes, dealers have bits painted out.

There are at least 7,000 antique dealers in Britain alone, but only a small percentage will be covered by the newly revised code of the London and Provincial Art and Antique Dealers' Association (LAPADA). Anyway, as one dealer put it: 'If you're straight, you're straight; if you're dishonest, you'll shield behind a code of practice.'

Although there are plenty of reputable dealers who liaise closely with museums and are respected scholars, anyone can set up as an antique dealer. It requires no training or qualification, nor even a shop or stall.

Criminals appearing in court for handling stolen goods often give 'antique dealer' as their occupation. 'It's like prostitutes describing themselves as models,' said one respected dealer.

There are many tales of dealers 'improving' works and it is not unusual for strange 'marriages' to take place: in one case, only one of four table legs was from the century to which the piece was dated. To cover himself, the dealer sold it as 'restored'.

Some dealers 'suggest' a date for a piece of furniture by placing a clipping from an old newspaper or document inside it. According to one story, a dealer placed a snippet from a 1791 copy of the Times in a chest of drawers of a later century.

Criminality among disreputable dealers ranges from commissioning robbers or forgers, to not rejecting stolen items. Some have been known to falsify a piece's provenance - for example, having documents faked. There are tales of dealers who, when someone brings a painting to them for restoration, have it copied, keep the original and let the owner take home the copy.

In obtaining new stock, a technique said to be used by the shadier members of the trade goes something like this: a dealer makes an offer for a piece of furniture. 'I'll give you pounds 500 for it,' he says. The wary owner wants to get the piece valued first, but when he is told that it is worth no more than pounds 150, he gladly calls the dealer back and sells it.

The dealer says, 'While we're at it, I'll offer you pounds 350 for that painting.' As the owner is so pleased to be making a profit on the furniture, he does not question the offer. He does not realise that the dealer only ever wanted the painting, which may be worth pounds 5,000.

The LAPADA charter says that members must not make unsolicited calls on houses. But there are dealers, known as 'knockers', who sweet-talk their way into homes. They tend to prey on the elderly.

Brighton is a main area of operation. One dealer travels round telling old ladies that their furniture has been requested for an exhibition run by the Queen. It works.

Another knocker will enthuse about a piece of furniture, telling the owner it is worth hundreds. Then he bends down and scatters sawdust underneath it. 'Oh dear, riddled with woodworm,' he exclaims. 'Not worth anything. I'll take it off your hands for pounds 50.'

Or he uses large grey maggots instead. 'You've got the Australian maggot,' he tells his terrified victim.

In a few cases, collectors deserve the dishonest dealers. A buyer who asked a dealer for two receipts, one for himself and a phoney one for export, was told he could buy a blank sheet of headed notepaper: 'To you, pounds 100.'