Autumn 1940: the Front Line is now Britain itself. Cities are blitzed night after night and even after the bombers have turned for home, a deadly menace remains: thousands upon thousands of UXBs. Buried underground, their clocks ticking remorselessly, unexploded bombs blocked supply routes, emptied hospitals and left families refugees. Dealing with this threat soon became Churchill's priority.

This desperate struggle became a battle of wits that pitted German ingenuity against British resourcefulness, including such extradinary figures as Robert Davies GC, who saved St Paul's Cathedral, and John Hudson, the modest horticulturalist who mastered the V1.