Real Tigers, by Mick Herron

This is the third of the, to date, eight Slough House novels (following Slow Horses and Dead Lions). Again, the TV version - which I saw first - is a pretty close adaptation, though as always the things that are different are intriguing.

The failed, disgraced agents exiled to Slough House plod on with their lives. But when Catherine Standish is kidnapped, River Cartwright is instructed to steal the vetting file on the Prime Minister from MI5 headquarter, the Park. Yet this mission is not all it seems. Leading figures in the service and government and making plays for power...

It's a fast-moving, twisty adventure full of memorable characters and nice subversions of what we expect - indeed, at one point River and fellow agent Louisa Guy note that their battle with villains right by a working railway line should have ended with someone being squished by a train, as it's the kind of thing that happens in fiction.

But then there's the way the book uses the fact that it's fiction. In the second book, a non-existent cat prowls the floors of Slough House, providing a perspective on each room and its occupants. Here, the observer passing unseen through the same building is a ghost - but we learn this person is a ghost now but they were alive when they journey up the stair. It's a thrilling moment as we realise what's going on, followed by a typical bit of dark humour from slovenly Jackson Lamb. I can see why this isn't in the TV version; it specifically works in prose, with a third person omniscient narrator able to see beyond the grave.

The other big difference is that the TV version includes a pretty big role for James "Spider" Webb from the previous two adventures, whereas in the book we hear about but don't see him. And the TV version includes stuff that is setting up the next story - the TV version of which concludes this week. I'd love to know more about the mechanics of adapting these books, the choices made to suit the strengths of TV, the things done for more prosaic, practical reasons.

We can also see Mick Herron revising his creation as he goes. I said that first novel makes little effort to obscure the real-life character on which MP Peter Judd is based. Here, alongside Judd's continuing ambitions for power, we get fleeting references to "Boris", so the two men coexist. We didn't know when we were well off.

Oh, and Seán Barrett is a great choice of reader for the audio versions of the novels. I knew him from Father Ted and from voicing Captain Orion in Star Fleet and Tik-Tok in Return to Oz. But he's had the most amazing career, such as playing Timothy opposite Patrick Troughton's St Paul in the BBC's Paul of Tarsus (1960). A picture of him taken during production of Dunkirk (1958) was used on the cover of the Smiths' single, Who Soon is Now?