Brian Braddock was born into the British high society, although his parents were really from OtherWorld. He studied Physics, and was working in a research center, until one day he had a dangerous accident and met Merlin, who offered him the chance to live in exchange for fighting as his champion. Brian went to Other World and stayed there as Captain Britain for a time. Later, he returned to his own dimension and to Braddock Manor, to live with her sister Elizabeth. It was then when he first changed his costume and met Meggan, his girlfriend.
After some adventures, he tried to retire, being substituted by his sister, but she lost her eyes fighting against the Master Assassin, and Brian retook the cape of the Captain, killing him.
During the Fall of the Mutants, Brian saw Betsy death on TV and disappeared (by the time, he had also a drinking problem), so Meggan went to Muir Isle to ask for help. Then, Phoenix (Ray Summers) appeared, chased by some war dogs, and after teaming with ShadowCat and Nightcrawler to rescue her, he became the brand new leader of Excalibur.
Brian acted dummy for a long time, being discovered later that he has been charmed to be clumsy, and getting rid of the spell thanks to Roma. He changed again his costume during The Crosstime Capers issues.
During a time, things seemed to work O.K., but his powers began to blink, supposed to be linked somehow to British territory. Later, he get lost in time and space, being rescued by Phoenix, who changed her place with him, and returning with another costume and a new name: Brittaniac. He seems to be far more powerful now, and also less human. Since he has traveled through time, he's supposed to have seen the future, but he can't tell in which temporal line things are going to happen.