I am known, where I am known at all, as Andrew Norton. (They tell me that I make a fleeting appearance somewhere in Alan Moore’s League of Extraordinary Gentlemen.) I’ve been away from London for years, on the south coast, the Balearic Islands, Crete, Istanbul, Beirut, Egypt: teasing connections between half-revealed mysteries, scraps of erased text, rumours in cafés. And always with the haunting sense that my efforts are doomed, the stories I recover have already been told. The world is nothing more than a confirmation of what it is. The perfect map of a deleted city. Tales of detection on rapid rewind. Self-justifying confessions of those who have already been found guilty and executed. Hackney: reservation of weary ghosts. Year zero. The final commission.

Simple technique for a simple place: make recordings, eavesdrop in pubs, markets, hospitals, Turkish cafés. On buses. Park benches. Betting shops, bingo halls. Estate agents, immigration solicitors. Bicycle repair shops. Outside mosques. In graveyards. Stay on the move, camera at the ready. Record signs, messages, small revisions in the fabric of things. Capture every security camera that captures you. Make your chart a palimpsest of revisions and quotations. Say nothing that hasn’t been said before.

Walk, every day, all day. Start from the same point and mark your unknown destination with a rose. Leave a diary of the journey in a Jiffy bag, an old tin, a bottle. Bury it, if you will. Collect information left by others, from the Fellowship of the Rose, in dead-letter drops: hollow trees, alcoves alongside railway arches, missing bricks under canal bridges. Tattered manuscripts wedged between slats on park benches.

In early May last year, coming through Victoria Park, at first light, I found a black bag on the plinth that supports one of the twin dogs with smashed snouts. Inside was a child’s diary of a camping trip to Epping Forest with the Wolf Cubs. And a floppy disk, titled in hesitant capitals: J.W. SICKERT TAPES. There was also a torn photograph of the Old Rose Pub on Ratcliffe Highway and some handwritten text about the head of Emanuel Swedenborg.

…Swedenborg was buried in a vault beneath this altar. In 1908 his body was exhumed and returned to Uppsala… The skull, so it is rumoured, was mislaid… Was the pillaged head fated to become a Masonic resource, boxed in black velvet in the depths of…

There was documentation pertaining to Hackney, affairs of the council, building contracts. In the bottom of the bag were curls of – probably – dog hair. A Mason jar of black cherries which turned out, on later inspection, to be preserved cockroaches.

In Milan, thanks to contacts at the university, I met a man who might have been Umberto Eco. I wanted to find out how serious the semiologist (and conspiracy freak) was about The Name of the Rose. My contact told me to carry a copy of London for Stalkers, which was credited to Nicoletta Vallorani.

After a very long evening, no food, gallons of black coffee, I heard more than I wanted to know about Rosicrucians, Cathars, the Priory of Sion and the sacred measurements of Templars. This was the event that brought me home: the Templars were a real presence in Hackney. Temple Mills. Well Street. They were deeply embedded…