In the new year of 1944 the French Resistance in northern France was on its knees. Relentless attacks on its diverse and disorganised networks by the Gestapo and the Abwehr had put many of its best operatives in prison, or worse. But in the lead up to Operation Overlord, ''D Day'', the Resistance had never been more important to the Allied war effort, and many groups were in the pay of Britain''s Secret Intelligence Service, MI6.

One such was organised by a patriot called Dominic Ponchardier. For months he had watched helplessly as his friends and colleagues had been swept up by the Nazi drag net, and cast into the old prison on the eastern outskirts of Amiens. In desperation he asked his MI6 handlers for help, and once London agreed it led to one of the most daring missions of the war.

On the morning of 18 February 1944, nineteen Mosquito bombers flew at low level across the channel, skimming just above the ground to drop their bombs on sections of the walls of Amiens Prison. Hundreds escaped, scores of whom evaded recapture to continue the fight against Nazi repression.

It was an epic of precision bombing, in which one of the most notable RAF heroes of the war, Group Captain Charles Pickard, lost his life. Robert Lyman''s book reveals, from previously unseen sources, the full truth of MI6''s involvement in the French Resistance, and narrates in vivid detail a stirring tale of courage and skill.