Book excerpt: Autumn 1940: The front line is Britain itself. Cities are blitzed night after night. Even after the bombers have turned home, a deadly menace remains: thousands of UXBs. Buried underground, clocks ticking. Unexploded bombs blocked supply routes, emptied hospitals and turned families into refugees. Dealing with this threat soon became Churchill's priority.It was a battle of wits, German ingenuity against British resourcefulness. This desperate struggle against the ticking clock is told through the experiences of four key figures; Robert Davies, who saved St Paul's Cathedral; Stuart Archer, protector of the vital Welsh oil refineries; the extraordinary Earl of Suffolk, who inspired The English Patient and made possible the atom bomb; and John Hudson, the modest horticulturalist who mastered the V-1.