My intention was only to pop into Evans Cycles in Holborn for a quarter of an hour and from there to carry on down to South Kensington on the Piccadilly Line. Yet, here I am on the corner of Shaftesbury Avenue and Charing Cross Road, about to embark on another of my spur-of-the-moment “walking adventures”. This time the object of my exploration is Soho. Not in-Soho, but outer-Soho. Its periphery, its urban borders; the imperfect rectangle that means so much to misfits and outsiders.

Not that it was always that way. Henry VIII’s former Royal Park’s delusions of grandeur were dealt a reality check with each…