Mackenzie Crook is an English actor, director and writer. He played Gareth Keenan in The Office, Ragetti in the Pirates of the Caribbean films, Orell in the HBO series Game of Thrones, and the title role of Worzel Gummidge. He is also the creator and star of BBC Four's Detectorists (2014–2022), for which he won two BAFTA awards. He also plays major roles in TV series Britannia, as the opposite leading druids Veran and Harka.

Gareth Keenan is a fictional paper salesman on the BBC's comedy The Office, portrayed by Mackenzie Crook. Gareth is a self-important team leader proud of his alleged Lieutenant status in the Territorial Army. He spends his days annoying his co-workers at Wernham Hogg with his rigid enforcement of the rules and sycophantic attitude towards David Brent, whom he views as a friend. Gareth describes his job title as "Assistant Regional Manager", but Brent often corrects this to "Assistant to the Regional Manager". His counterpart on the US series is Dwight Schrute. The character was originally meant to be a tough military character but, after Crook's audition, Ricky Gervais and Stephen Merchant decided to reinterpret the character.