To Inspector Lucas Rocco, the gathering in the churchyard looked too casual to be a riot, too small to be a funeral. Newly exiled from his home base in the Clichy-Nanterre district of western Paris under Interior Ministry orders, and assigned to the village of Poissons-les-Marais, in Picardie, north-west France, it was a welcome distraction. He turned off the car radio, killing in mid-sentence Johnny Hallyday, the current singing heart-throb de choix, and left his Citroen Traction outside the local cafe to find out what was commanding such a gathering in this flyspeck of a place.

‘It’s a bomb, I tell you.’ A compact, nut-brown man in a greasy old bush hat was speaking round a spit-stained Gitanes with the assurance of one who knew about such things. The focus of everyone’s attention was a large, cylindrical object lying in a shallow depression in the chalky soil next to the gravelled pathway. Tapping the rusted metal casing with the toe of his boot brought a sharp intake of breath among the crowd, who all stepped back a pace.

‘Probably from the Great War,’ said a phlegmatic woman in a black headscarf and chequered apron. She stood hugging an armful of leeks to her ample bosom like a character from an old painting. ‘It looks old enough.’

‘No way,’ Bush-hat disagreed. ‘Those little kites wouldn’t have been able to lift anything this big.’

‘Doesn’t look that much to me,’ muttered an old man in traditional bleus — the uniform jacket and baggy trousers of the working man in rural Picardie. In spite of the warm weather, the trousers were tucked into a pair of enormous rubber boots, the tops reaching his knees.