An "amicable" arrangement was said to have been reached between Mr McEwan and his former wife, Penny Allen, who disappeared with the boy on Thursday just before a court in Guingamp ordered her to return him to his father. An order was issued by the court for her arrest and she was traced in early evening to the neighbourhood of Saint Brieuc, 50 miles away. Ms Allen told gendarmes she feared being separated from her son.
Last night, Ms Allen said she had been arrested while cycling with her son between Saint Donan and Callac. She said she had spent Thursday night in a small hotel in Saint Brieuc, and the following morning they bought two mountain bikes.
She said that she had been treated well at the police station and that her son had signed a statement saying he wanted to stay with his mother.
She now faces another court hearing in Oxford on Monday, which will consider the conditions attached to an injunction taken out by Mr McEwan forbidding Ms Allen and her companion, Ismay Tremain, from "harassing" Mr McEwan, but Ms Allen said she did not recognise its jurisdiction.
Earlier, gendarme sources said that she was being sought for the "kidnapping" of the boy, under French law. But last night a senior officer at the Callac gendarmerie station - where the reconciliation occurred - near Guingamp, said that she had been allowed to go to her home in Bulat Pestivien, 12 miles away. He said it was unlikely that charges would be brought against her.
The writer Timothy Garton-Ash, who is a friend of Mr McEwan and travelled to Brittany with him, last night appealed for the father and son to be left in peace. He asked the press to allow Mr McEwan "some time to be with his son after the ordeal that he has been through".
The hunt was sparked on Thursday after the court at Guingamp issued an arrest warrant for Ms Allen when she failed to obey a judicial order to return the boy to his father.
Ms Allen appeared briefly at the court on Thursday morning but left before the judgment that ordered her to return her son to Britain. During the afternoon, gendarmes, accompanied by Mr McEwan, visited the house where Ms Allen and the boy had been staying in Bulat Pestivien. There was no sign of the mother or child but Mr Tremain, was taken to the station at Callac for questioning. He was released yesterday.
The boy was supposed to have been returned to his father on 16 August after spending six weeks with his mother. Mr McEwan's 15-year-old son had already returned from the holiday to his father. In March, Oxford County Court granted Mr McEwan sole and permanent custody of the younger child.
Mr McEwan is well known in France. His novel A Child in Time won the Prix Femina for the best foreign novel in 1993. The book, about a child whose custody is disputed by his parents, was translated into French under the title L'enfant vole (The Stolen Child).