When Rousseau fled to England in 1766 he brought with him his dog Sultan but left his companion Thérèse Levasseur to follow along later. Perhaps he should have been more careful, especially with men like James Boswell loose on the Continent.

JB had been doing the Grand Tour, during which he looked up Rousseau and Therese at Môtiers in Switzerland. He poured the usual dollops of enthusiasm over Rousseau and watched politely as Sultan was sung to and made to perform a ballet. He also watched Thérèse with some interest, describing her as 'a little, lively, neat French girl'.

She was forty-three at the time and had been with Rousseau for twenty-two years. As a servant girl she had been bowled over by the philosopher, who seemed not to worry about her lack of education but treated her very much as an equal. In return she cooked for him, guarded his privacy and adapted herself entirely to his strange way of life. She also accepted his opinions about people and, since he was won over by the boyish charm of Boswell, so was she. When Boswell left on the next leg of his tour he gave her a garnet necklace and expressed the hope they would meet again.

This happened sooner than he expected. He was in Paris, mourning the death of his mother when he encountered Thérèse, who was wondering how to get to England. 'Mon Dieu, Monsieur, we could go together?' ...