A grandfather who worked as a bank clerk during World War II stopped vital information making its way to Hitler's Germany while posing as a Gestapo agent.

Eric Roberts, born in Wivelsfield, East Sussex, in 1907, served as agent Jack King to infiltrate UK fascist groups while working at Westminster Bank for the Euston Road branch.

He was recruited in the 1920s by British spymaster Maxwell Knight who is believed to have inspired James Bond character M in the 1930s.

Eric Roberts, born in Wivelsfield in 1907, served as agent Jack King to infiltrate UK fascist groups while working at Westminster Bank at the Euston Road branch

During his work he gained the trust of 500 Nazi sympathisers and prevented information being leaked including the British Union of Fascists led by Oswald Mosley in the 1930s.

The family lived in Epsom, Surrey, before settling in Nettlestone on the Isle of Wight.

He took early retirement aged 49 in 1956 and moved with his wife Audrey with children Max, Peer and Crista to Vancouver, Canada.

However his family were unaware of the extent of his espionage until it was published in National Archive papers in 2012.

And even his son Max, 84, knew little about the double life his father led.

Grandaughter Marilyn, 45, from Toronto, Canada, told the Daily Mirror: 'As a child I knew grandad was a spy during the war but our family had no idea what that really involved.'

Sir Oswald Mosley walking down an avenue of saluting Blackshirts when he arrived the Albert Hall in April 1934

British spymaster Maxwell Knight who is believed to have inspired James Bond character M in the 1930s

She recalled how as a child she would make up adventure stories with her cousins about her grandfather's double life.

Marilyn said how her father remembers her father disappearing for days but was unaware of what he was doing.

She said her father recalls having to walk five feet in front of Eric when in London and was told to hand over the phone when it rang.

In 1968 MI5 contacted Eric after British intelligence officer Kim Philby and those who were part of the Cambridge Spy Ring.

Philby was exposed as a double agent who passed information to the Soviet Union during the war.

He was questioned by officers regarding his wartime activities and died four years later aged 65 after the worry affected his health.

The book bears similarities to Amazon drama 'Hunters' where Al Pacino (pictured) leads a team bringing US Nazis to justice during the 1970s

Author Robert Hutton published a book in 2018 on Eric's life named 'Agent Jack – The True Story of MI5’s Secret Nazi Hunter' after approaching the family.

It relates how MI5 fooled dozens of British fascists into believing they were spying for Germany.

Hutton said: 'People ­trusted Eric implicitly. He was fantastically ­outgoing, a real practical joker and very charming. His personality got him out of a lot of scrapes.'

In the book it tells how Eric managed to calm a gang of fascists in Leeds in 1940.

It also bears similarities to Amazon drama 'Hunters' where Al Pacino leads a team bringing US Nazis to justice during the 1970s.

The group discovered he had given a false job and address however Eric told how he was 'able to set their mind at ease'.