His father was a Jewish tailor's machinist who, to escape anti-Semitic pogroms, had emigrated to London with his wife, whose maiden name was Lifschinska, from Łódź, Poland, around 1900.

It was a bad time for Jewish immigrants and refugees who arrived in Britain during this period: antisemitism was both in the streets and the corridors of power.

Proving his abilities as a street fighter, Comer soon joined Alfred Solomon's gang, The Yiddishers, and saw a route out of poverty.

[4] Rapidly becoming a powerful force in the East End, and having built a reputation running "muscle" in Leeds, Birmingham and other northern nightclubs, Comer and his gang began to violently take control of racecourses across Britain.

A wartime effort to crack down on illegal gambling clubs led to Jack and several companions being rounded up and then conscripted into the army.

His discharge was formally for 'mental instability,' but in fact he had beaten an antisemitic superior officer, and continued to make himself a nuisance until he was released.

Under Comer's leadership criminals such as Billy Hill, the Kray twins and Freddie Forman were able to rise in London's underworld.

[8] In 1956, Comer and his wife were ambushed and viciously attacked by a group of eight men armed with clubs and knives about 100 yards outside their Paddington flat.

[9] Whilst Comer was recovering from his injuries, his enemies "grassed him up" to the police for attacking and cutting a petty criminal, Tommy Falco.

[11] Comer is mentioned in the 1985 song "Ghosts of Cable Street" by The Men They Couldn't Hang, where he is referred to as "Jack Spot".