| Spoiler warning!|
Plot details follow.
"Shanker", whose real name is never mentioned, is a former flatmate and long-time ally of Cormoran Strike. He works in the illegal drugs trade, has spent half of his adult life in prison, and often provides Cormoran with information about the locations of wanted criminals for a £500 fee.
Shanker is tall, pale and lean. His head is shaved and he has tattoos covering his neck, wrists and knuckles. He is freckled and has a gold tooth and a deep facial scar that twists his upper lip and runs to his cheekbone. He dresses casually and smells strongly of cigarette smoke, cannabis and body odour.
Shanker is originally from Canning Town but his cousins from Whitechapel were gang members, and his choice to help them against rival gang members led to him gaining the scar across his face, (though he stabbed his attacker in the thigh). It was while lying in the gutter with his bleeding injury and under the influence of a drug that he first met Leda Strike. Leda brought him to her home with fellow seventeen-year-old Cormoran and then boyfriend Jeff Whittaker, taking care of his injuries as best she could. Thankful for her kindness, Shanker frequently visited her, sharing with Cormoran a mutual dislike for Whittaker and wariness of her abusive boyfriend. Whenever the intimidating (and less restricted by social norms) Shanker was around, Whittaker did not dare to treat him as badly as he treated Cormoran, even refraining from needling Cormoran while Shanker was around.
Shanker's recurring presence in Leda's home made Cormoran feel comfortable to leave for university, knowing that Shanker would keep her safe from Whittaker in his absence. Unfortunately, while Shanker was away on a trip for a drugs deal, Leda died, supposedly from a heroin overdose. He returned to news of her death and—like Cormoran—believes Whittaker to have killed her. At Whittaker's trial for Leda's death, Shanker was called as a witness and could not remain composed, shouting at Whittaker across the court room and openly accusing Whittaker of Leda's murder.
- Cormoran privately admits to no longer remembering why Shanker is called by that nickname and even why Shanker calls him Bunsen in return.
- Shanker is first mentioned in The Cuckoo's Calling but never by name, only appearing in discussion with Cormoran over the phone—when he provides Cormoran with leverage over a police officer.
- Cormoran suspects that Shanker has begun a relationship with Alyssa after chasing away Broadbank from her home.