This will be the fourth outing for the series of spy stories that couldn't be further from the world of James Bond. It's broadly based on Mick Herron's fifth Slow Horses novel Spook Street. As always, at the centre of the story are the group of MI5 agents exiled to Slough House, because they're regarded as, frankly, pretty rubbish by the rest of the service. If it closely follows the book, Jack Lowden's River Cartwright will face up to difficult family issues, while we'll see a new side to Gary Oldman's flatulent Jackson Lamb.

Read More