Doctor Who fans watch 50th anniversary special
Doctor Who fans have praised the show's 50th anniversary episode as "epic" and "phenomenal".
The Day of the Doctor was broadcast in 94 countries at the same time as it aired on BBC One on Saturday night.
Featuring three Doctors - Matt Smith, David Tennant and John Hurt - it delved deep into the character's psyche over 75 minutes.
There were also cameos from former star Tom Baker, and Peter Capaldi, who replaces Smith later this year.
"It's the most ambitious episode we've ever done," said the show's boss, Steven Moffat, ahead of the premiere.
Opening with the show's original credit sequence from 1963, the special featured the Daleks and the return of shape-shifting aliens the Zygons, who first appeared in 1975.
But the principal villain was potentially the Doctor himself.
Moffat's story played with the idea, introduced when the science-fiction show re-launched in 2005, that the Doctor was the "last of the Time Lords".
It transpired that Hurt's version of the Doctor had taken the decision to commit mass genocide in order to halt a "Great Time War" - and the 75-minute episode saw him fighting to come to terms with that decision, aided by two future versions of himself.
"The last few minutes affected me quite deeply," wrote Neil Perryman on the Guardian's website.
He conceded that some of the details "didn't make a lot of sense on first viewing" but added: "I don't care - I'll be watching it again this evening".
Speaking immediately after the show ended, star Matt Smith said: "I think what's really clever about it is that what he [Moffat] has managed to do is change the mythology of the character - which, after 50 years, is an achievement."
Aside from the emotional drama, the episode was filled with comedic moments - including a proposal, a marriage and "a machine that goes ding".
When Hurt's Doctor met his frenetic, childlike future selves, he asked: "Am I having a mid-life crisis?"
The show was also crammed with special effects, leaping from modern London to the planet of Gallifrey and Elizabethan England.
"I don't think it bears any resemblance to what we were doing," said Carole Ann Ford, who starred in the very first episode 50 years ago.
Screened in 3D in more than 1,500 cinemas in 94 countries - from Russia to Ecuador - the episode attracted hundreds of fans in fancy dress, from bow ties to Dalek outfits.
A gala screening at the BFI in London was attended by Smith, Hurt, Moffat and their co-star Jenna Coleman.
A huge cheer echoed around the cinema as the end credits rolled, while Tom Baker's surprise cameo also received a large round of applause.
The reaction on Twitter was similarly ecstatic.
Karl Purdon wrote: "That was simply phenomenal", while Freema Agyeman, who once played Martha Jones in the series, called it both "epic" and "compelling".
Moffat said the special episode had been partly conceived as a way to explain the gap in the series' history - from its cancellation in 1989, until the re-launch, under Russell T Davies, in 2005.
"I knew I wanted to make it about the Time War, and I wanted that 16-year gap to mean something," he said.
"There was a whole other Doctor we got conned out of".
Speaking before the broadcast, Moffat - the show's lead writer and executive producer - admitted he was "nervous" about the scale of the special.
"I'm glad we don't do it every time, but it's very exciting to do it once," he told the BBC News website.
He said he hoped fans would be "very happy", adding: "It's got a big emotional wallop at the end".
Moffat described the first ever Doctor Who episode, An Unearthly Child, broadcast on 23 November 1963, as "one of the very best episodes of Doctor Who ever made".
"All the ideas come from there," he said.
"The music, the name, the Tardis, the police box bigger on the inside... in terms of brand new ideas that's a rollercoaster of 25 minutes."
Moffat, along with Matt Smith and Jenna Colman, attended the official Doctor Who anniversary celebration at London's ExCel on Friday.
The three-day event, which is being attended by 8,000 fans a day, features appearances from Doctor Who stars from all eras of the series.
American Richard LeCour said he made a special trip from his home in California because Doctor Who had been "part of my life for 40 years".
Adam Highway, from Brighton, predicted that Doctor Who still had a long future ahead of it.
"It'll go on as long as it keeps that balance of appealing to people who don't know the history, but respects the history for those who give a damn about it," he said.
"I think Steven Moffat's got it spot on."
The anniversary story was Matt Smith's penultimate outing, before he regenerates at Christmas into a new Doctor, played by Peter Capaldi.