Chemical Mitch was a loan shark who appeared in Series 8. After getting conned on a drug deal with Welsh boys, Shane Maguire was forced to borrow a large amount of money from him. Jamie warned that Chemical Mitch was so named for his use of battery acid, which he was known for throwing at both his enemies, and his enemies innocent family members.

Jamie Maguire suggested that the Welsh Boys had been working with Mitch, stealing from Shane on his orders knowing that he would go to Mitch to borrow money, whether this was true or one of the many lies Jamie was telling Shane in order to gain control of the family business is unclear. Nevertheless, Jamie took Shane to kill Mitch, supplying a gun and talking him into it. Shane struggled with himself for a while before Jamie won him over, and Shane shot Mitch dead. Shane never forgave Jamie for talking him into committing murder, something that he could never forgive himself for either. This proved to be Shane's first foray into murder, but certainly not his last.