From TARDIS Index File, the free Doctor Who reference.

Donna is convinced to turn right, rather than left when she was supposed to.

Donna's World (a.k.a "Turn Right") was a rewritten version of the official timeline created when Donna Noble turned right instead of left while deciding which of two different job interviews to attend. As a result, the Doctor never met Donna and died underneath the Thames Barrier. He also never met Martha Jones. These events resulted in devastating effects for Earth and the universe.

This name is conjectural.

History

While on the planet Shan Shen, Donna was unknowingly fitted with a time beetle, part of the Trickster's Brigade. A fortune teller selected a point in her life where making seemingly random choice had enormous ramifications.

In June 2007 Donna had to make a choice between two jobs. The moment she chose between the jobs was at a junction. Her agency had offered her a contract with H.C. Clements, which while temporary, was posh and in the centre of London, which Donna enjoyed. Her mother, Sylvia Noble, had managed to get her another job opportunity to become the personal secretary of Jival Chowdry, owner of a photocopying business. Although this would be a permanent job, Donna found it less interesting.

While driving and in discussing the dilemma, Sylvia pressured her into turning right to stop by Jival Chowdry for a chat. While in the regular timeline Donna ignored her mother and turned left, in this timeline she turned right, resulting in her taking the PA job. (DW: Turn Left)

Timeline

December 25, 2007

The Doctor is dead...

The Doctor tracks down the Empress of the Racnoss to the Torchwood base underneath the Thames Barrier and blows it up, which floods the whole thing. Although the Empress of the Racnoss and her offspring drown, the Doctor is unable to escape and dies too quickly to regenerate. Donna stumbles across Rose Tyler, who has arrived on the scene too late to do anything. The Doctor's TARDIS is salvaged from under the Thames and sent to a UNIT base in Leeds. (DW: Turn Left)

In the original timeline, the Doctor met Donna Noble who saved his life when she told him to stop after the Doctor blew up the Torchwood base. Also, there was a hole drilled to the centre of the Earth so the hole may have been sealed off. Rose Tyler is not believed to have been present in this timeline. (DW: The Runaway Bride)

2008

Oliver Morgenstern, the final survivor of the Royal Hospital tells the World what has happened on the Moon.

The Judoon H2O Scoop the Royal Hope Hospital to the Moon to find a Plasmavore criminal and her Slab accomplices. Although they found and killed the alien criminals, the Plasmavore had already armed the MRI. Sarah Jane Smith, Luke Smith, Maria Jackson, and Clyde Langer, who had been in the hospital when it was transported, managed to disarm it; but they died, along with the rest of the hospital, when their oxygen ran out. The only survivor was Oliver Morgenstern who was passed the last oxygen tank by medical student Martha Jones, who gave up her life to save him. (DW: Turn Left)

In the original timeline, the Doctor investigated the hospital instead of Sarah Jane, Luke, Maria and Clyde under the alias "Mr Smith" and no one suffocated because he found the Plasmavore in time. Shortly after, he took on Martha Jones as a companion. (DW: Smith and Jones)

Because those events hinged on the Doctor meeting Martha Jones, in this timeline, the events created by Harold Saxon also would never have occurred and the Archangel Network or the Valiant were never designed or built, among other changes such as Captain Jack Harkness never reuniting with the Doctor. The status of certain other events post-Thames Barrier such as the incident with the Weeping Angels (DW: Blink) remain unclear, especially in the aftermath of Dec. 25, 2008 (see below).

Rose Tyler visits Donna and advises her to persuade her family to spend Christmas some place other than London. (DW: Turn Left)

December 25, 2008

Mushroom cloud from Titanic impact

A replica of the Titanic crash-lands onto Buckingham Palace and destroys the Greater London Area and floods the whole of Southern England with radiation. Donna's family, who did decide not to stay in London for the holidays, having won a luxury getaway in a raffle, watch the events on television and are able to see the mushroom cloud of the explosion from a distance. (DW: Turn Left)

In the original timeline, this crisis was averted thanks to the Doctor. Although the city was nearly abandoned in the main timeline, this seems not to be the case here. Also, The Doctor had stated that if the Titanic crash-landed on Earth, it would wipe out all life, but it appears he was mistaken or exaggerating, as only southern England was affected directly. (DW: Voyage of the Damned)

2009

The Adipose wreak havoc in the United States.

England has come under martial law in order to deal with the crisis caused by the nuclear explosion. The United States promises fifty billion pounds in financial help for Great Britain but this plan has to be abandoned when sixty million Americans are fully converted into Adipose children. Miss Foster's plan is not only successful, but sixty times as successful as was planned in the real world.

In the original timeline, the Adipose plan targeted Great Britain and was stopped before it was put in full swing thanks to the Doctor and Donna Noble. The change in location was due to England no longer being viable for breeding due to the nuclear disaster.

Rose and Donna see Torchwood Three save the world, at the cost of their lives.

The Sontarans activate the ATMOS devices in the cars to convert Earth into a breeding ground. The surviving members of the Torchwood 3 team work (presumably with UNIT) to stop the scheme. The team destroys the Sontaran flagship and successfully revert the atmosphere to its previous state, but Gwen Cooper and Ianto Jones die in the attempt; Jack Harkness, being immortal, survives and is captured by the Sontarans and transported to Sontar as a prisoner. Britain is largely unaffected due to its poverty and hence its lack of vehicles with ATMOS devices. Rose Tyler once more appears to Donna to try to persuade her to help change back the timeline. (DW: Turn Left)

Without "Harold Saxon" to design it, the UNIT vessel the Valiant, which helps turn the tide against the Sontarans in the original timeline, is never built. In the original timeline, the Sontaran invasion of Earth was prevented by the Doctor, Donna, Martha Jones and UNIT. The Doctor was able to clear the atmosphere without the assistance (or sacrifice) of any Torchwood members. (DW: The Sontaran Stratagem/The Poison Sky)

Roughly three weeks after the Sontaran Invasion, the British government makes a new law ("England for the English") forcing all non-British citizens in Britain to go to "labour camps". Donna's grandfather laments that "he never thought he would see this happen again", and and when Donna chides him, saying that they are just relocation camps, he replies that "that's what they said last time". Soon afterwards, the stars begin going out. (DW: Turn Left)

After the timeline is corrected, the stars' fading is discovered to be an effect of the reality bomb. (DW: Journey's End)

Rose Tyler, through methods and reasoning unknown, is working with UNIT on reverse-engineering the TARDIS, creating a time machine with which Rose hopes to restore the timeline.

Rose's relationship with UNIT is unique to this timeline, as there's no indication that she ever worked with the UNIT of the normal timeline.

Negation

Alternate Donna dies.

UNIT and Rose Tyler sent Donna back to the point where the timelines diverged. According to Rose, in order to restore the timeline, Donna had to make her past self turn left instead of right at the point where she decided whether to follow her mother's advice or her own instincts. Donna arrives in 2007, but too far away from her past self to directly influence her; instead, she orchestrates an accident by stepping out in front of a lorry, which blocks traffic and forces the earlier Donna to turn left. Just before her death, Rose Tyler appears and whispers a message for her to give the Doctor when the timeline is fully restored. (DW: Turn Left)

Behind the Scenes

• It is not actually a parallel world since the walls between realities were sealed in Doomsday. This was made explicit by the production team. Rather it is an altered version of the Doctor's world. According to quantum physics, every decision we make creates multiple realities - one for each option of that decision. This theory implies that, despite the timeline being restored, the Donna's World reality still continued to exist in some form.