John Maughan, 40, vanished with the 300-year-old instrument as Min-Jin Kym stopped for a sandwich at Euston Station, London, on November 29.
Miss Kym, 32, was sitting with her cellist boyfriend when Maughan and his cousins, aged 16 and 14, took the Stradivarius, one of only 450 in the world.
Victim: The court heard that, for internationally acclaimed musician
Min-Jin Kym, the violin 'is her life'The musician said the violin was ‘her life’ but it has not been recovered, despite a nationwide Crimewatch appeal.
Police recognised career criminal Maughan from CCTV and he was arrested with his cousins.
Blackfriars Crown Court heard that Dublin-born Maughan has received ‘every sentence the courts can give’ for 123 separate convictions.
The violin was in a case with two bows – one made by Peccatte is worth £62,000 alone.
The gypsies tried to sell the instrument for £100 to a man in an internet cafe in Tottenham Court Road where they were researching ‘Stradivarius’ and ‘1698’.
Insurers have offered a £15,000 reward for information on the violin, which Miss Kym purchased for £750,000 a decade ago.
All three defendants admitted theft. The 16-year-old was given ten months’ detention and the younger boy, now 15, was referred to a youth court for sentencing.