Dickens now did something extraordinary. Nine months before he finished Pickwick Papers, this man of prodigious energy, only twenty-five years old, began to write Oliver Twist, one of the world’s most famous novels, whose ‘Please, sir, I want some more’ is familiar even to the millions who have never read it. And then, five months after he completed Pickwick, he started his third novel, Nicholas Nickleby, before Oliver Twist, his second, had reached its halfway point.

Throughout his life, peripatetic residentially as well as psychologically – living at over two dozen London addresses in a half-century – Dickens covered the whole of London, from the East End and the City, north to Camden, through Westminster and west to Hammersmith, south along the shores of the river. Even when he was officially settled, he frequently maintained several addresses at once, some known to his friends and family, others more or less kept hidden.

But other types of walks had other purposes. There was the ‘straight on end to a definite goal at a round pace’ walk, and the ‘objectless, loitering, and purely vagabond’ walk: walking to get places, and walking for the fun of it, for looking, and for being looked at. Many people did both, but it may be that Dickens wrote more about walking and wandering than anyone else. ‘Whenever we have an hour or two to spare, there is nothing we enjoy more than a little amateur vagrancy – walking up one street and down another, and staring into shop windows, and gazing about as if, instead of being on intimate terms with every shop and house…the whole were an unknown region to our wandering mind.’ According to his contemporaries, he was ‘on intimate terms’ with almost every district. A man who had worked with him when he had been an adolescent solicitor’s clerk said, ‘He knew it all from Bow to Brentford.’ Four decades later, at the end of his life, they were saying the same: give Dickens the name of almost any street and he could ‘tell you all that is in it, what each shop was, what the grocer’s name was, [and] how many scraps of orange-peel there were on the pavement’. His London, in the words of a reviewer, was described ‘with the accuracy of a cabman’.