Josephine was a Wren who drew maps for D-Day, while Penny was an officer in the First Aid Nursing Yeomanry. In their late 90s, they're in huge demand - rolled out at every memorial service and WW2 anniversary, and popping up on red sofas and at literary festivals all over the country. Journalists and producers love them, as does the Great British Public. Despite their age, they're still in great nick - sprightly and sparky, and always up for whatever the next excitement might be. And now they're off to Paris to receive the Légion D'Honneur for their part in liberating France.

The sisters have fond memories of the City of Light and of August Samuel, a young Jewish man they met there in 1939. August died fighting for the Resistance, while his mother and sister disappeared after the notorious Vel d'Hiv Roundup. Penny believes they were denounced by their Parisian neighbours for the sake of a priceless emerald ring.

Penny has always been cagey about her war effort. Under her FANY cover, she was actually an SOE agent, risking her teenage life in France alongside the likes of Violette Szabo and Odette Sansom. After the war Penny found a more lucrative application for the skill set she'd acquired - as a very successful international jewel thief. Now the Samuel family's looted jewels have resurfaced in an auction to be held in Paris on the day of the sisters' investiture. Can a much loved and much decorated (but frankly ancient) veteran, dressed exclusively by M&S, avenge her old friends, and pull off one last daring heist?