The jaw of the 13th century preacher and theologian, a contemporary of St Francis of Assisi, was on permanent display in a shrine in the Capella del Tesoro in the Basilica in Padua, his adopted home town. On 10 October 1991 four men held up the congregation in the church, smashed the shrine and ran off with the relic. A waiting car drove them away.
Police appeared to be getting nowhere with their inquiries, until on 20 December 1991 they made the dramatic announcement: the bone had been found in a field near Rome's Fiumicino Airport. In the nick of time, they said, they had managed to stop it being put on a plane bound for a Colombian drugs cartel. The chief of police, General Antonio Viesti, took the bone from Rome back to Padua in triumph.
Curiously, no arrests were made. Details about who wanted St Anthony's jaw - and why - were sketchy.
In fact, the police story was a complete fabrication. The bone was stolen to order for the Italian Piovese Mafia family. Soon after the jaw was taken, police were contacted by a well-known mafiosi from Ferrara. He was put in touch with the Italian secret service in Bologna.
The deal he offered was remarkable: return of the relic in exchange for the head of the Piovese family not being sent to jail. The authorities say they refused to make such a promise, but Gennaro Egidio, a leading Rome lawyer, says he has learned that assurances were given. The jawbone was dropped off near a rubbish tip in Ponte di Brenta and the Piovese di tutti capi has not been seen since.
Last month, a Mafia informer named General Viesti, the former commander- in-chief of the carabinieri, and the head of the Religious Artefacts Protection squad, Colonel Conforti, as being part of the cover-up, of having falsified documents to push through the bizarre trade and concocted the story of having discovered the bone at the airport. A secret inquiry led by examining magistrate Maurizio Gionesini, has been launched. General Viesti and Colonel Conforti have been arrested.
Mr Egidio, who is defending them, has secured the release on bail of the policemen, whom he suspects have been made scapegoats by the authorities. The recovery of the jaw at the airport, Mr Egidio said, was "a bluff to cover the counter-espionage services".
Dubbed "Perry Mason all'taliana" by the local press, Mr Egidio believes the disappearance and subsequent appearance of St Anthony's jaw could be among the worst of the many scandals to have hit Italy, involving the mixing of the secret service and Mafia with part of a popular saint.
Only last month, the vocal chords of St Anthony, known in the Catholic Church as the patron saint of lost objects, were on tour in Britain. They were venerated in Masses in London, Manchester and Glasgow.