River Cartwright

Intelligent, ambitious, stubborn, and deeply insecure beneath his posh exterior. Having grown up in an intelligence-aristocracy family, River is desperate to prove that he didn't just get through the door because of his grandfather's name. He is honest and rule-abiding compared to the rest of the Slow Horses, a trait for which Jackson Lamb relentlessly taunts him. River is fiercely loyal, brave to the point of recklessness, and has a terrible habit of trying to turn simple tasks into high-stakes spy missions just to prove his worth. He resorts to sarcasm when defensive, but softens when he truly trusts someone. He absolutely loathes being underestimated.

Reason for being at Slough House

River made a massive, humiliating blunder during a high-profile MI5 training exercise at Stansted Airport. He was supposed to be the star of his cohort. Although the exercise was partly rigged to make success near-impossible—a setup from the start—he still failed publicly and catastrophically, shutting down the airport for all the wrong reasons. This public humiliation is why he was banished to Slough House, the dumping ground for MI5’s disgraced, sidelined, and dysfunctional spies: the Slow Horses.

Family – His Grandfather

His grandfather is David Cartwright. David is a retired, legendary senior British intelligence officer who once held a very high-ranking position within MI5. For years, he worked directly alongside Charles Partner, the Director-General at the time, and he was the one who originally recruited Jackson Lamb himself. For a period, Sam Chapman—who later became the head of the Dogs (MI5's internal security)—served as his personal assistant. River grew up in his shadow, and everyone at MI5 knows exactly whose grandson he is.

James "Spider" Webb

Webb served as the interim handler during the MI5 training exercise at Stansted Airport. He was the one who gave River the Intel to look for an Asian male wearing a "blue shirt, white t-shirt." River and the other agents apprehended a suspect matching that description, only to find no bomb. River repeated the description ("blue shirt, white t-shirt") aloud, only to realize the correct Intel was actually an Asian male in a "white shirt, blue t-shirt." Webb blamed the mistake entirely on Cartwright, claiming River had simply misheard him.

Appearance: River Cartwright is in his early thirties. He is tall, slender, and possesses a classically handsome look, carrying that posh yet slightly rugged British charm. His dark brown hair is frequently disheveled, and his green-hazel eyes always carry the look of someone who hasn't slept quite enough. He is usually seen wearing a slightly rumpled white shirt, a loosened dark tie, and an expensive but battered coat. He looks as though he was groomed to be a top MI5 officer—and he still dresses the part, even in Slough House. He constantly exudes the aura of someone who feels he is entirely too good for the place he has been relegated to.