According to the publisher, there are eight novels in the Slow Horses series, but there are several other novels and novellas set in the Slough House world. They are written by Mick Herron, contain characters such as Jackson Lamb and River Cartwright, and so we are going to consider them canon. People get really hung up about canon so what I mean in practical terms is that I am going to try to read them in order, inserting them as appropriate into the main eight books. (There is a prequel, Reconstruction, but I didn’t know about it at the time so will come back to it later.) The List was written in 2015, between Dead Lions (novel 2) and Real Tigers (novel 3). (There’s a further standalone novel, Nobody Walks, which comes immediately after The List. Keeping up?)

The List is a quick and enjoyable read which clocks in at 96 not-very-closely-typeset pages. It covers the tale of dead asset Dieter Hess and the discovery by Diana Taverner that he’s been receiving mystery money. His handler, John Bachelor, has to scramble to find out what is going on before Taverner casts him out of the service without a pension. (The possibility of his becoming a slow horse is raised by Bachelor and dismissed by Taverner. Bachelor is worse than the horses.)

This is a great story of almost-analogue spy tradecraft. There’s a cribsheet with a cipher and a code, hidden under a carpet. Bachelor ropes in help: a newbie psychologist, whose quest to find out what Hess was up to leads him to the great Molly Doran and, in turn, Jackson Lamb.

Although this is a short little thing, there is plenty of room for Herron to entertain us. He gives us an idea for arranging a home library: forget alphabetical order, Dewey decimal, size or (shudder) colour: place the great Russian authors in order from best to worst. He points out that the booze Lamb has drunk during the time Catherine Standish has been in recovery would float a hippo. He gives us little hints at doing spyfare better – including giving an actual example of how Hess had not followed ‘Moscow Rules’, and what it means to trade in false information. And, just as he does in the main novels, he makes us complicit in a world of deceit, such as when he suggests (via Diana Taverner) that anyone would jump at the chance of rifling through their best friend’s cupboards. Speak for yourself, Lady Di. New fella J K Coe visits Slough House and notes its aromas: coffee, stale bread, takeaway food, cardboard, grief. 

I enjoyed this chance to go beyond what I’ve first encountered on the TV screen. Indeed, anyone who has watched the Apple TV adaptation and doesn’t want to read the novels as they follow a similar plot line, could happily start here.

UPDATE 16 June 2025

I revisited The List as I was reading The Drop, a second novella to feature John Bachelor. Here are some additional observations:

First, although The List contains Diana Taverner, Jackson Lamb, Catherine Standish and Molly Doran among its characters, Herron’s style is slightly different from that which he employs in the main novels. (Though one of the pleasures of reading Herron is seeing how he mixes it up as the series develops.) He seems to take less joy from his observations. One of the themes of the series is that spy craft is just a great game – an earlier novel sees it portrayed as secondary school shenanigans with geopolitical effects – but The List really drives home how the incentives provided to individual operators can make or ruin the lives of random colleagues. Catherine Standish and Molly Doran might know how to deploy Lamb to provide information to other members of the service, but even though they therefore build up a network that is able to call in favours, an individual like Bachelor is able to mess things up quite merrily for others without serious consequence for himself.

Second, I didn’t know when I first read The List that we would meet a few of the characters again: in particular J K Coe. It is worth reading The List purely for the introductions. And once you have done so, you should absolutely carry straight on with Nobody Walks.

Our other Slow Horses/Slough House coverage:

Slow Horses

Dead Lions

Nobody Walks

Real Tigers

Spook Street

London Rules