London Rules

London Rules is the fifth novel in Mick Herron's Slough House series, first published in English in 2018. The Simplified Chinese edition, translated by Li Yang, was released by New Star Press in July 2025 as part of the Midnight Library · Slough House series. The story is set in Britain after the Brexit referendum: at MI5 headquarters in Regent's Park, London, the new Director-General Claude Whelan is struggling to adjust to a position few would envy—he must keep a beleaguered Prime Minister safe, contend with politicians who are using the Brexit turmoil to stir up trouble and eye 10 Downing Street, and face a lawmaker's wife who publicly rails against him in the tabloids. Most unnerving of all is his deputy, Diana Taverner, whose sharp eyes are always watching for his mistakes. Worse still, a string of seemingly random terrorist attacks is spreading across Britain. Meanwhile, in Slough House, the spies' place of exile, each member of the Slough House team is mired in his or her own difficulties: one is sunk in pain, another is battling addiction, and another suspects the new colleague is a dangerous lunatic. Fate is ironic: it is these discarded "slow horses" who are drawn into a crisis that will affect both politics and public opinion, and they prove in their own inimitable way that things can always get worse. The "London Rules" of the title refer to the unspoken rules of bureaucratic self-preservation and shifting blame at the first sign of trouble, as opposed to the "Moscow Rules" of always watching for a knife in the back. With biting British black humor, Herron weaves political infighting, media noise, and espionage operations into a dark comedy of the disenchanted.