When Jennifer Lockley was growing up in the 1950s, a salesman came to the door of the family home one afternoon.

He was selling pots and pans and was pushy and aggressive. When Jennifer's mother, Irene, tried to close the door, he stuck his foot inside to stop her.

Jennifer never forgot what happened next. In one rapid manoeuvre, her housewife mother sent the salesman sprawling, somehow throwing him — and his pots and pans — across the front garden. 

He picked himself up, shaken and utterly flabbergasted, and fled.

Jennifer was too small then to ask her mother about it, but many years later — not long before Irene died — she summoned her daughter and, over an aperitif, told Jennifer the incredible reason that she knew how to floor a man with the flick of her wrist.

Irene had been recruited into a top-secret underground guerrilla unit during World War II known as Section VII. 

She and her fellow recruits — many of them teenagers like her — all signed the Official Secrets Act, and most never breathed a word about their clandestine wartime activities, which have remained largely hidden from view until now.

For a few, like Irene, confided their secret just before they died. 

Author Andrew Chatterton has pieced together the story of Section VII and other shadowy wartime organisations, and reveals this intriguing hidden chapter of the war in a new book Britain's Secret Defences: Civilian Saboteurs, Spies And Assassins, to be published later this year.