Banks (John Blundell) is known to his stooges as 'Pongo', and is the antagonistic former 'Daddy' of the wing that Carlin is sent to.
Tall, surly and hostile, Banks dominates A-wing accompanied by two other bullies (Richards and Eckersley) and has an arrangement with the warders to keep 'order' and gain a percentage of other inmates money and tobacco.
Banks uses strength to bully inmates, including Carlin, who is subjected to a severe beating upon his arrival in the dormitory after Banks was tipped off by warder Mr Greaves about Carlin's arrival and history. This and other incidents later provoke Carlin to take over as the 'Daddy'.
After hitting Banks' main toady Richards with a sock containing snooker balls (and threatening his other stooge Eckersley when he tries to run away and warn Banks), Carlin returns to the dormitory area to find Banks in the bathroom, midway through a wash. Carlin dunks Banks' head in the basin, cutting his head on the taps, and repeatedly punches and kicks him, declaring himself the new 'Daddy'.
Because of favouritism in the borstal, corrupt warder Mr Sands knows it was Carlin who beat up Banks and Richards and wants Banks to name Carlin as the culprit. However, Banks, bleeding profusely and in obvious pain, is reluctant and insists he 'slipped'. This is a common thread throughout the movie - when violence is discovered by the warders, the victim, who is unwilling to be a rat, does not name the perpetrators, but just claims to have 'slipped,' no matter how much of a state they're in when discovered.
Once Banks is admonished by Mr Sands, Richards and Eckersley continue to victimise some of the younger inmates (such as Jackson and Rhodes) claiming that Carlin will be released before any of them, and therefore leaving the way open for their return to power. Banks, however, is only seen in the film again at the end when the inmates pray for their dead colleagues (in the television play it's made clear Banks is in hospital, in the theatrical version this is not revealed).
"There's very stiff penalties for anyone who tries to undercut my rate...you make sure certain parties know that, Dougan!"
"There's no dolly mixtures in here, pooftah!"