Had he but known that before the day was over he would discover the hidden dimensions of the universe, Kit might have been better prepared. At least, he would have brought an umbrella.

Like most Londoners, Kit was a martyr to the daily travails of navigating a city whose complexities were legendary. He knew well the dangers even the most inconsequential foray could involve. Venturing out into the world beyond his doorstep was the urban equivalent of trial by combat and he armed himself as best he could. He had long ago learned his small patch of the great metropolitan sprawl; he knew where the things most needful for survival were to be found and how to get to them. He kept in his head a ready-reference library of street maps, bus routes, and time schedules. He had memorised the pertinent sections of the London Underground tube schematic; he knew the quickest ways to work, and from work to his favourite pubs, the grocers, the cinema, the park where he jogged.

Sadly, it was rarely enough.

This morning was a perfect case in point. Only minutes before, he had stepped out the door of his flat in Holloway on a jaunt to accompany his girlfriend on a long-promised shopping trip. Oblivious to the fact that he had already embarked on a journey of no return, he proceeded to the nearest tube station, flapped his Oyster card at the gate, stormed down the stairs as the train came rattling to the platform, and leapt aboard as the beeping doors began to close. He counted off the first two of the four stops to his destination and was just allowing himself to imagine that all was running according to plan when he was informed at the third stop that the line was closed ahead for routine maintenance.

“All passengers must change,” crackled a voice through tinny loudspeakers. “This train is terminated.”