Hero published by Marvel Comics. Captain Britain first appeared in the U.K. in Captain Britain Weekly #1 in 1976 and in the United States in Marvel Team-Up #65 in 1978.

Among the myriad of dimensions in the Marvel Universe exists a dimension called Otherworld. This dimension has in the past been ruled by Merlyn, the wizard who was a companion of King Arthur and later by his daughter Roma. From this dimension came an agent of Merlyn to live in the dimension of Earth. This agent adopted the guise of James Braddock, who during his life excelled in scientific pursuits and eventually was made a knight. Sir James and his wife had three children: Jamie, the eldest and fraternal twins, Elizabeth and her brother Brian.

Brian grew up and favored his father in his love of and mastery of science. Brian excelled in school and was a quiet and unassuming child. After college, Brian was hired by the Darkmoor research facility, one of Britain's leading scientific thinktanks. Braddock had been working there only a few months when late one night the facility was attacked by the forces of a villain known as the Reaver. Despite the fact that most of the staff was killed and the facility itself was nearly utterly destroyed, Braddock managed to escape. Pursued by agents of the Reaver and almost mortally injured, Braddock stumbled into a site of ancient standing stones where he saw Merlyn and Roma, who offered him the choice between two mystic items: the amulet of right and the sword of might. Having just seen what force would do and possessing a deep sense of justice, Braddock chose the amulet of right and was instantly healed and transformed into Captain Britain. Armed with his magic sceptre, Braddock was able to fly, had super-human strength, enhanced speed, and superior endurance. Braddock defeated Reaver's agents and began to adventure around England.

For a short time, Braddock moved to the United States in an exchange program based in New York City. Strangely enough, Braddock ended up rooming with a student from Empire State University who worked as a photographer for the Daily Bugle named Peter Parker. This lead to at least one adventure in which Spider-Man, Parker's other identity, and Captain Britain fought against the villain Arcade (as seen in Marvel Team-Up #65).

While returning to the United Kingdom, Braddock believed he was being attacked by mystical forces and threw himself from the plane in which he was traveling. He survived this when Merlyn pulled him from our time and sent him into the past to fight along side the time-displaced hero the Black Knight. Merlyn also provided Captain Britain with a companion in the form of Jackdaw, an elf from Otherworld. The trio fought against Necomon and eventually defeated him.

Merlyn then sent Braddock to another dimension's Earth where all the heroes had been killed by a mutant who could change reality with his mind called Mad Jim Jaspers. During the journey to this world, Merlyn took the abilities of his septer and put them into a new costume. Captain Britain and Jackdaw teamed with Opal Luna Saturnyne, who was from another reality as well, in trying to save this world. The trio was attacked by a creation of Jasper's called the Fury which was supposed to be the ultimate killer. Saturnyne fled while Jackdaw and Captain Britain battled the creature. Both Jackdaw and Captain Britain were killed during this battle, but Roma and Merlyn took Braddock's remains and rebuilt him without the memories of his death and returned him to Earth.

Braddock was taken to Otherworld where he learned that he was one of many Captain Britains that existed across the multiverse. This Captain Britain Corps had a strict set of parameters and code of conduct, all of which Brian rejected. He chose instead to work as a free agent independent of the Corps.

During this time on Earth, Brian met a metamorph named Meggan and was forced to work with an agency of the British government assigned to deal with superhumans called the RCX. The RCX began to manipulate Captain Britain, forcing him to open up his ancestral home to it for use as a haven for children effected by the manipulations of Mad Jim Jaspers. These children or warpies as they became known because they were effected by Jasper's reality changing ablility called the Jasper's Warp were being turned over to the RCX because they could not be raised by their parents. Eventually, the RCX caused Braddock to step down as Captain Britain. Braddock left his home and traveled with Meggan, while his duties as Captain Britain were taken over by his sister Elizabeth or Betsy, who was a powerful telepath.

During her tenure as Captain Britain, Betsy Braddock was attacked by one of her brother's old foes, a man called Slaymaster. The two battled, but the new Captain Britain was no match for her foe and he blinded her by gouging out her eyes. Her telepathic cry was heard by her brother, who came to her rescue. He battled with his old foe, killing Slaymaster in the process and retaking the mantle of Captain Britain.

For a time, Braddock and Meggan lived in a lighthouse together until they were drawn into active service again as part of Excalibur. Joined by a number of former X-Men, Captain Britain adventured with the team for many years, until it was discovered that they were being manipulated by Merlyn into helping destroy divergent timestreams to add to Merlyn's power as the guardian of the multiverse. Captain Britain along with Excalibur were able to stop Merlyn's ploy and return things to normal.

Later, Braddock was lost in the time and when he was recovered through the efforts of his teammates, he possessed additional powers and called himself Britannic. During his time as Britannic, Braddock possessed all of the powers of Captain Britain, but also had a heightened sixth sense like Captain Marvel's Cosmic Awareness. Braddock was also extremely cold and distant and this put a strain on his relationship with Meggan, his fiance. Eventually, Braddock used his newfound powers to aid in turning back an attack by the extraterrestrial menace of the Phalanx. Battling the Phalanx caused Braddock to lose his new abilities and afterward, he took a leave of absence from Excalibur as well as from being Captain Britain.

Braddock aided Excalibur in their investigation of the British black-ops group Black Air and their work with the Inner Circle of the Hellfire Club. Braddock used his family connections to infiltrate the Inner Circle and during that time created a new costume that allowed him to have all of his original powers but to also create a forcefield for protection as well as offensive use.

Soon after, Braddock and Meggan married on Otherworld and Excalibur disbanded. The newlyweds were drawn to Otherworld soon after when an intelligent computer created by his father called Mastermind began to kill off the members of the Captain Britain Corps, in the guise of Roma. During the battle with Mastermind, Braddock pulled the legendary sword Excalibur from a stone and used it, along with the help of others, to defeat Mastermind. He then took over as the guardian of the multiverse.