Joe Country, by Mick Herron

In the depths of a London winter, life is looking even more bleak than usual for the stable of dud MI5 agents at Slough House. River Cartwright’s venerable grandfather has died and his errant father shows up to spoil the funeral. Louisa has been guilted into chasing up her dead lover’s missing son and Catherine is at risk of falling off the wagon. The latest slow horse, Lech, may be guilty of a heinous crime, or may have been set up. Diana Taverner has finally achieved top dog status at the agency and quickly embodies all the maxims on power, while maintaining her determination to obliterate Slough House. Herron uses recent British history, with its dodgy populist politicians and seedy royals, to highlight the deficiencies of the security services in a declining democracy. One interesting angle is the impact of Brexit, with former European allies not only stopping cooperation but becoming potential antagonists. Almost all of the slow horses are at risk of becoming casualty of the week in this book, and the suspense of who succumbs is maintained until the end. This is a particularly brutal and bloody sequence of events, again ending in a cliffhanger that calls into question the future of the Slough House, with Taverner tempted down a very slippery slope.