Ten years older than his siblings, Brian and Betsy, Jamie learned his brother had become the superhero Captain Britain when Brian stopped a possessed Betsy from killing them both on behalf of Dr. Synne. Later, Jamie was also peripherally involved in Brian's battles with the Red Skull, Lord Hawk and Slaymaster; however, after Brian went overseas and Betsy's modelling career took off, Jamie lost touch with both of them.
Addicted to his racing career's rich lifestyle, Jamie took a bribe from the criminal Maggia organization to lose a race, then won anyway. To repay them he took illegal jobs, using his racing as cover to travel the world; minor crimes became increasingly lucrative and immoral ones, until he was trading in human lives. Jamie was eventually captured by Joshua N'Dingi (Dr. Crocodile); learning from Crocodile of Jamie's activities, Brian left him to his fate. Trying to mystically cure Jamie's evil nature, Crocodile's Witch Woman instead unlocked his latent mutant powers, but the magic which held him also bound these. Dimensionally displaced despot Sat-Yr-9 hired the Technet to free Jamie, knowing her reality's version of him possessed powers; left insane by his torture and believing he was living in a dream without consequences, Jamie entered her service. He helped Sat-Yr-9 take over the crimelord Vixen's organization, and targeted his brother's team Excalibur, empowering an otherworldly counterpart of his to battle them. He later clashed with Alfie O'Meagan, an other-dimensional reality warper, which briefly put him off playing with alternate Earths.
Eventually, Sat-Yr-9 ambushed Excalibur and Betsy, now the X-Man Psylocke, in Braddock Manor. Jamie slew their ally Alysande Stuart, and then tortured the captives for hours before Meggan broke free and attacked him, breaking his concentration. Psylocke rendered Jamie comatose with her psychic knife. Sat-Yr-9's troops fled, taking Jamie with them, though his unconscious form somehow ended up at Excalibur's Muir Island base, where his siblings attempted to reach him telepathically.
Recently, Jamie appears to have awoken. Marvel Girl (Rachel Grey) and Psylocke have caught glimpses of him, and he prevented Saturnyne (a counterpart of Sat-Yr-9) from destroying Earth-616 (his home reality). He seems to be manipulating events, possibly in connection with the recent reappearance of another reality warper, Mad Jim Jaspers, an old foe of Brian's; but his true motivations remain unrevealed.