Sebastiano Saia, who was born in Sicily, was arrested on Friday night as he sat with his girlfriend in the Pizzaria Marina.
He now faces extradition to Italy to face charges in connection with smuggling 500kg of heroin into his country from Turkey.
A spokesman for the Rome- based central anti-drugs agency said it was claimed that Saia was a leading member of the Calabrian mafia, the N'drangheta.
'He is one of the biggest catches we have ever made. You have to realise the size of the drugs charge against him. It is 500 kilos - half a tonne - it's enough to addict a whole nation.'
He said Saia was in England as an 'ambassador' for N'drangheta to track down pounds 2bn in cash which had gone missing. The money disappeared when police cracked another drugs smuggling ring.
Saia, 47, also described as a financial adviser, was arrested in a joint operation between Metropolitan Police officers and drugs squad detectives from Rome. He appeared at Bow Street magistrates' court on Saturday on the extradition warrant, which said he was wanted in Italy in connection with drug smuggling. He was remanded in custody while Italian lawyers complete the paperwork before his extradition.
Scotland Yard said the extradition warrant was acted upon on behalf of the Italian government and Saia was sought in connection with drug smuggling in Italy. He was allegedly a senior member of the gang involved.
A businessman in the area, who would not give his name, said: 'He came into my place about two weeks ago. He just came in to introduce himself and say hello. He said to me 'I am the new owner of the pizzeria'. We only spoke for a couple of minutes. He seemed quite ordinary and was quite nice to me.'Reuse content