The BBC was founded in 1922, becoming government owned in 1927.
The following year in 1928, the worlds first television show, 'The Queen's Messenger' would air across the pond in Schenectady.
ITTL, Have the first director of the BBC go out on a limb, wanting to really start something special and new and fund something similar. As for his character;
"His goal was to broadcast "All that is best in every department of human knowledge, endeavour and achievement.... The preservation of a high moral tone is obviously of paramount importance."
As a result, this pioneering show would likely have education at the forefront. What is a BBC founded show that was initially founded on education, and has since become one of the longest running shows ever? Doctor Who!
And so we end up with:
'Doctor Who?', 1928-present
Other names could be chosen (I'm quite partial to "The Long Way Round", but not really relevant).
By starting with education it can stay around in the early days when shows and films couldnt be too daring, slowly transitioning into a drama/sitcom/whatever the hell you classify Doctor Who as which elongates its staying power into the present.
By utilising the concept of regeneration, the show is able to continue on with different crews and actors, never leading to the common issue a lot of soap operas face (once they reach a certain age and characters have been around so long and have such interwoven, long-standing stories and relationships, it's hard for new viewers to get invested and understand context. For this reason, I struggle to see a soap staying around much longer than real world ones have).