He has spent more than a decade exposing the murderous criminal underworld of the Italian Mafia, but journalist Roberto Saviano believes that Britain is the most corrupt country in the world.

The author of international bestsellers Gomorra and ZeroZeroZero, has lived under police protection since publically denouncing members of the Camorra, a powerful Neopolitan organised crime syndicate, in 2006.

On Saturday he made a rare historic appearance at the Hay Literary Festival flanked by several security guards.

He warned the audience in Hay-on-Wye that financial institutions were allowing ‘criminal capitalism’ to thrive through offshore holdings. And he warned that a vote to leave the European Union would leave Britain even more exposed to the organised crime.

“If I asked you what is the most corrupt place on Earth you might tell me well it’s Afghanistan, maybe Greece, Nigeria, the South of Italy and I will tell you it’s the UK,” he said.

“It’s not the bureaucracy, it’s not the police, it’s not the politics but what is corrupt is the financial capital. 90 per cent of the owners of capital in London have their headquarters offshore.

“Jersey and the Cayman’s are the access gates to criminal capital in Europe and the UK is the country that allows it. That is why it is important why it is so crucial for me to be here today and to talk to you because I want to tell you , this is about you, this is about your life, this is about your government.