The slow horses are a group of MI5 rejects who have been condemned to Slough House (their name a pun on the building they work in) after messing up, but not enough to get fired. Here, this group of misfits grind though dull administrative tasks under the occasional verbal abuse of their boss Jackson Lamb (Gary Oldman).
The quick-witted spy thriller is back for its fourth season following this crew of pencil pushers as they manage to get involved in stopping plots that endanger Britain.
Mick Herron, the author of the Slough House series of novels, has been described as the modern John Le Carré. Le Carré (real name David Cornwell) was a former intelligence officer and the premier spy fiction writer of the Cold War and post-Cold war era. But the connection is unfair to both Herron and LeCarré.