William Hartnell (in-universe)

William "Billy" Hartnell was an actor in both the 20th and 21st centuries. He met the Sixth Doctor in the 1930s, was buried near to Ijezie Obiefune by the 1980s, and by 2065, was playing the role of Dr. Who in the television series.

Biography
By 1936, Billy had starred in films in produced in London, including I'm an Explosive and While Parents Sleep. Billy's friend, Max Miller, invited him down to Brighton to pick up some tips.

When Miller encountered the Sixth Doctor and Evelyn Smythe and began assisting them in their investigations of some mysterious murders and disappearances, Billy was entirely sceptical of the Doctor's stories of evil aliens and disappointed by Miller's willingness to believe them.

After the alien entity was defeated and the Doctor and Evelyn departed, Miller headed back to the pub to tell Billy all about it. (AUDIO: Pier Pressure)

By the 1980s, (COMIC: The Infinite Astronaut) W. Hartnell had been buried near to the grave of Ijezie Obiefune, which his daughter Alice and wife Ada visited often. (COMIC: Whodunnit?)

He was too busy to reprise the role in the theatrical film Dr. Who and the Daleks in 2065, leading to a new take on the Doctor being played by Peter Cushing in the film instead. (PROSE: Lady Penelope Investigates the stars of the Sensational new film Dr. Who and the Daleks!)

Alternate universes
William Hartnell also existed in an alternate universe where Doctor Who existed solely as fiction. In this universe, Hartnell starred in the series in the early 1960s, perhaps most notably in the lost serial The Outlaws. (PROSE: The Thief of Sherwood)

Information from invalid sources
Verity Lambert got the idea to cast Hartnell as the Doctor after seeing him in the kitchen-sink drama This Sporting Life. (COMIC: Doctor Whoah! 407) While spending Christmas Day aboard the Valiant, the aged Tenth Doctor wore a wig bearing a tag that read "Hartnell, keep". (COMIC: Doctor Whoah! 390)

Other matters

 * I'm an Explosive and While Parents Sleep were actual films made in the UK in the 1930s, both of which starred a young actor known as Billy Hartnell. In 1936, Hartnell was 28 years old.
 * This Sporting Life, a film that starred William in the real world, also exists in the DWU.
 * The information presented about Earth popular culture by TV Century 21 about such topics as the in-universe Doctor Who and The Avengers franchises is narratively discontinuous with most other stories, as TV Century 21 moved these series and others from 1965 to a hundred years in the future, 2065, creating obvious disparities with stories that didn't follow this creative decision.
 * It should be noted, however, that the dating for Thunderbirds is typically inconsistent, and many accounts date the series to the 1960s, meaning the discrepancies can be somewhat explained.