Slow Horses (Slough House Thriller 1) by Mick Herron – Kindle Edition

Slough House is the outpost where disgraced spies are banished to see out the rest of their derailed careers. Known as the slow horses these misfits have committed crimes of drugs and drunkenness, lechery and failure, politics and betrayal while on duty.
In this drab and mildewed office these highly trained spies dont run ops, they push paper. Not one of them joined the Intelligence Service to be a slow horse and the one thing they have in common is they want to be back in the action.
When a boy is kidnapped and held hostage, his beheading is scheduled for live broadcast on the net. And whatever the instructions of their masters at the Intelligence Service headquarters, the slow horses arent going to just sit quiet and watch.