When he was 14 years old the boy, Martin Nadaud, joined the other men on the long march, wearing his first-ever pair of boots: they made his feet bleed. Paris was a place of grinding toil and nights in lodgings where a dozen exhausted men snored together in one room. It was a world of insecurity and accidents, where wine and butcher's meat replaced the pancakes and goat-cheeses of the beloved homeland, and where the blood and barricades of the 1830 Revolution opened young Nadaud's eyes to worlds undreamed.
He was a tough boy like the others, but with an intelligence and ambition all his own. Gradually he taught himself not only the skills of masonry but to read and write properly. He taught his mates too, made contact with better-educated men in the Republican movement, and by the time the Revolution of 1848 sent France's last monarch hurrying into exile across the Channel, Nadaud was a revolutionary leader. The next year he became France's first working-class MP. The cartoonists had a field day, depicting him in a smock with a trowel in one hand and a Socialist manifesto in the other.
But the fate which had already caused him to live through three distinct identities - Creusois peasant, Parisian labourer, public figure - had several other lives in store for him. In 1851 when Louis Napoleon became Emperor, Nadaud found himself flung into prison, then exiled from France "in perpetuity".
Everything he had worked so hard to achieve was lost to him. Like many French political refugees before and since, he crossed the Channel; there, in London, on a rain-soaked building site in Islington surrounded by strangers with whom he had not a single word in common, he had to earn his living again in the only way he knew. Once more, he had to acquire a new language, literacy, a whole new set of customs and values.
He passed some hard, obscure years: his spirit nearly cracked. But then the story takes another turn. In his forties now, he abandoned the buildings to teach French - something he was at first convinced he could not do because of his lack of formal education. "I felt," he wrote, "like an impostor. A robber." And the plan did involve some pretence, since he was terrified that the parents of his pupils should discover that he had, not all that long ago, carried hods of cement on his shoulder. He persevered, boning up on history and grammar in the newly opened British Museum Library, and spent 12 years cramming French into future officers of the British army in a military school in Wimbledon. Here, he learnt to appreciate muscular Christianity - a concept then unknown in France. It was a whole other life for him, a reincarnation.
In 1870 when the Empire fell, Nadaud returned home in triumph and eventually settled down as a respected elder statesman. But to me this time in Wimbledon, no longer a patriot disguised as a workman but a workman disguised as the Frog teacher, is the most extraordinary of his whole career.
I have taken these years as the basis for a Radio 4 play, an imaginary drama in which, however, all the characters are real. So, for that particular life of Monsieur Nadaud, listen at 2.15 on 29 July.
Gillian Tindall is the author of `The Journey of Martin Nadaud: a life and turbulent times' (Chatto & Windus, pounds 15.99)