Exactly 50 years after the first episode was broadcast on November 23, 1963, Doctor Who show runner Steven Moffatt said the anniversary special would deliver an "emotional wallop" to millions of fans worldwide.
"It's the most ambitious episode we've ever done," he said.
The 75-minute special kicked off with Smith dangling from his Tardis spaceship - which has the form of a vintage British police telephone box - as it flew over London.
Traditional Doctor Who villains such as the Daleks and the Zygons also made an appearance, as did England's 16th century queen Elizabeth I.
Hurt was introduced as an incarnation of the doctor in an episode in May, while Tennant played the role between 2005 and 2010.
Doctor Who is the world's longest-running science fiction series, according to the Guinness Book of World Records, and has been sold by the BBC to more than 200 territories around the world.
The anniversary episode was broadcast in 3D in cinemas from Russia and Brazil to Spain and Sweden, as well as on British television.
Smith is to quit the show in a special Christmas episode, meaning another reincarnation that will usher in Scottish actor Peter Capaldi, best known for playing a foul-mouthed spin doctor in the BBC satire The Thick Of It.
There have been a string of events to mark the program's 50th year, including a three-day convention in London this weekend attended by some 20,000 fans.
US search giant Google also got into the act by changing its web page banner to feature cartoony images of a Dalek and the various doctors.
- AFP
