1949: in a still-Blitzed and shell-shocked London, the hapless and gormless Dennis Knuckleyard works as a bookseller (as a bookseller with subpar levels of hap and gorm myself, I can sympathise). A straightforward stroll into Soho to buy up some old Arthur Machen titles for the shop splays into nightmare when a dealer foists a physical book upon him that has previously only existed within Machen’s fiction.

So begins Knuckleyard’s initiation into the Other London or ‘Long London’: the mythic, magic city that burbles alongside the timebound, messy, everyday version – our version. Dennis stumbles his frightened and overwhelmed way into this hallucinogenic, fever-dream-haunted Other London, intent on ridding himself of the disturbing volume and returning to the ‘Short London’ of his normal life, as ugly and prosaic and unprepossessing as that life is.

But via his misadventures, he meets denizens of Short London, such as the charming Grace Shilling and the straitened Austin Osman Spare, the real world artist/magician whom Alan Moore has included in previous fictions. Although Dennis’s experiences in the Other London threaten and horrify him, its proximity pulls colour and friendship into his heretofore grey and lonely life.

Moore, best known for his literary approach to writing comic books (Watchmen, From Hell), has more recently turned to prose, including expansive novels (Voice of the Fire, Jerusalem) and conceptually rich short stories (Illuminations). His comics background persists into The Great When, with physical descriptions of the worlds of Short and Long Londons springing to life in both A–Z Guide to London street accuracy and acid-trip detail. Moore’s verbal sense of fun is in full flight, too: if I had my druthers, I’d shelve this book in our myth/geography/fiction/humour/history/occult area, if we had one. And the best bit? There are four more Long London novels to come: fall into this book and embrace a world of hilarious Cockney magic realism, with a roaring ‘To Be Continued’ emblazoned across the last page …