Spanner is a techie who helps Strike conduct forensics on Lula Landry’s laptop. He is described as a “pallid, straggly-haired young man” wearing “jeans, a psychedelic T-shirt, Converse sneakers, and a leather bag slung diagonally across his chest.” He has “a first-class degree in computer science” and treats technology with more interest than he does people.

Spanner calls Cormoran Strike by the nickname “Federico,” or “Fed” for short.

In The Cuckoo’s Calling, Strike and Spanner meet in a restaurant in London’s Chinatown called Wong Kei; here, while dining together, Strike gives Spanner Lula’s laptop. Spanner has a lager and a Wonton soup. When Spanner comes to Strike’s office later in the book, he flirts with Robin Ellacott and Strike warns him off of his engaged assistant.

In Lethal White we find out that Spanner is the younger brother of Strike’s old friend Nick Herbert. In this book it is mentioned how Spanner had overhauled their computer and telephone system.

In The Ink Black Heart, Spanner helps the detectives create a website for Robin to go undercover.