[5] The special also features the return of many other actors to the show, including Catherine Tate, John Simm, Jacqueline King, Alexandra Moen, Billie Piper, Camille Coduri, Freema Agyeman, Noel Clarke, John Barrowman, Elisabeth Sladen, Tommy Knight, Jessica Hynes and Russell Tovey.

The story features the Tenth Doctor (Tennant), who has been running from a prophecy of his impending demise, as he is drawn into a scheme by his old nemesis, the Master (Simm).

The Doctor saves Wilf by taking his place in the control room and suffers radiation poisoning, triggering a regeneration.

After returning Wilfred home, the Doctor visits his past companions: he saves Martha and Mickey, now married, from a Sontaran; prevents Luke Smith from being hit by a car and bids farewell to Sarah Jane; connects Jack with former midshipman Alonso Frame; meets Joan Redfern's great-granddaughter and inquires if she led a happy life; sees Wilf one more time to give him a winning lottery ticket for Donna as a wedding present; and briefly visits Rose the year she is due to first meet the Ninth Doctor.

One of the two dissident Time Lords, described as "The Woman" in the credits, visits Wilfred on several occasions, appearing and disappearing in unexplained ways.

British newspapers The Daily Telegraph identified the character as the Doctor's mother as early as April 2009,[6] with the episodes' writer Russell T Davies writing in an email to journalist Benjamin Cook, "...

"[10] Davies had been planning the story for some time, indicating that it continued the trend of series finales being progressively more dramatic: I knew I'd write David [Tennant]'s last episode one day, so I've had this tucked away.

[1][14] The last three specials of 2009 are foreshadowed in the episode "Planet of the Dead", when the low-level psychic character Carmen gives the Doctor the prophecy, "You be careful, because your song is ending, sir.

Because when we come back in "The Waters of Mars", it's all become a little bit darker.Julie Gardner – And as we know, David, he really does knock four times.Tennant – Yeah, absolutely, and if you think you've figured out what that means, you're wrong!Gardner – But when you do figure it out, it's a sad day.Writing in his regular column in Doctor Who Magazine issue 416, Davies revealed that the original title for "Part One" of "The End of Time" was "The Final Days of Planet Earth", while "Part Two" was always referred to as "The End of Time".

[17] Due to the sheer scale of the story, however, it was decided that both instalments needed the same title, differentiated by part numbers,[17] the first such instance since Survival.

Davies's script for the second episode finished with the Tenth Doctor's final line, "I don't want to go", followed by action text describing the regeneration and ending with the words "And there he is.

[22][23] John Simm, who played the Master in the 2007 series finale episodes "Utopia", "The Sound of Drums" and "Last of the Time Lords", was spotted on location during the Tredegar House recording.

[36] Due to the special effects used to simulate the violent nature of the Tenth Doctor's regeneration, the glass central pillar in the middle of the TARDIS console was damaged so badly it had to be rebuilt prior to the recording of the next series.

[37] A teaser trailer, featuring Timothy Dalton's opening narration and brief shots of the main characters, was shown at Comic-Con 2009.

[38] A 'Next Time' trailer, consisting some of the Ood Elder's monologue with excerpts from various scenes in part one, was included at the end of "The Waters of Mars".

[40] Additionally, the 2009 Christmas idents for BBC One featured David Tennant as the Doctor using the TARDIS as a sleigh pulled by reindeer.

Concurrently with the recording of the story, a music video was produced, featuring the cast, extras, crew, and Adipose, all lip-synching and dancing to The Proclaimers' 1988 song, "I'm Gonna Be (500 Miles)".

[42] When simulcast HD figures are added to the BBC One transmission, Doctor Who actually comes out as the most watched show on Christmas Day with a total of 12.04 million viewers, narrowly ahead of The Royle Family and EastEnders.

The episode achieved a 35.5% share of the total viewing audience on an evening where an estimated 30 million viewers were watching TV in the UK.

Robins notes that the first part had been "a rush" and questions whether any previous Who story managed to erase the entire human race before the end of the first episode or done it in such a comic and Christmas friendly way?

Robins also notes that Cribbins seems to be playing the same role that Tate did by "becoming the tragic hero while remaining the comic relief."

[47] Andrew Pettie of The Daily Telegraph states that his Doctor Who revelation came in the nick of time after previously thinking that the show was overrated.

Commenting on Cribbins' performance, Pettie states that he cut a King Lear like figure and notes that the Master's plan was evil even by his standards.

Pettie notes as the credits rolled his thoughts turned to the dramatic shortcomings of the show before realising that the "true brilliance of Doctor Who can only be felt if you're experiencing it in the company of wide-eyed seven-year-olds", a comment which he likens to Christmas itself.

But on a side note Lawson states that the script seemed to be modelled on Hamlet, a role which Tennant took on both on stage and on TV during 2009.

"[50] In his review of Part Two published the day after transmission, Andrew Pettie of The Daily Telegraph awarded a rating of four stars out of five, summing up the episode as "a barnstorming hour of family entertainment."

Despite expressing slight dissatisfaction with the plot, which he perceived as excessively complicated, Pettie admitted that the episode "charged forward with such apocalyptic brio it was hard to be unduly worried about what, precisely, was going on."

Praising Tennant's final performance as the Doctor, he also commented on the "unnerving experience" of seeing the character so helpless in his final appearance, but ended his review on a note of optimism for the future of the series with a new lead actor: "[Matt] Smith's youth and lack of fame make his Doctor Who an exciting prospect.

Both parts of "The End of Time" were released on DVD in the UK in January 2010 as a double pack with "The Waters of Mars".

"The End of Time" is also part of the special 50th Anniversary Regenerations DVD box set and book collection released on Monday 24 June 2013 and limited to 10,000 copies.