He was brought up in Woolwich and joined the Royal Marines at the age of 16. Maslen sustained an injury whilst in the Marines, resulting in him having to leave. Maslen is a vegetarian and has a six-year-old son named Zak.
After being injured while serving in the Marines, he went to Miami at 18 to see where fortune lay and was spotted by photographer Bruce Weber, and he earned a successful career as an international model, travelling the world earning "a good living" in glamorous locations.
Five years later, he turned to acting and landed a role in the successful television series Lock, Stock... in 2000. He has also played the live action rendition of Claude Speed in DMA Design's promotional video and opening sequence for Grand Theft Auto 2. After a few more television and film roles he landed his part in The Bill in 2002.