Ninth Doctor (The Curse of Fatal Death)

A Time Lord calling himself the Doctor travelled in the TARDIS with his companion Emma. After an encounter with his old enemies, the Daleks and the Master, he regenerated four times in quick succession, ultimately transforming into a female body.

A day to come
When the Eighth Doctor looked into the Tomorrow Window, he saw several possible ninth incarnations, one of whom was "a listless-looking man [who] sat on a sofa beside a girl in a red dress in an unconvincing medieval dungeon". (PROSE: The Tomorrow Windows)

Adventures with Emma
At some point, the Doctor began travelling with the "glamorous" Emma (PROSE: Who's After Your Cash) in whom, "without even knowing [he] was looking", he found "a woman to love". The two developed a romantic relationship, with the Doctor's next incarnation later indicating that the two had had sex at least once. (TV: The Curse of Fatal Death)

Coming back to Earth for the first time in many years, the Doctor became aware of a charity event centred around a "TV spectacular" which, among other things, contained a depiction of his and Emma's adventures battling the Daleks and the Master. He wrote a rambling latter to The Mirror endorsing the production and insisting that readers give what they could to those in need. In this letter, he described himself as "over 800 years old". (PROSE: Who's After Your Cash)

Death
The Doctor wanted to settle down in domestic bliss with his companion Emma, and he invited the Master to meet him on the planet Tersurus to inform him of his retirement. On Tersurus, both Time Lords had travelled back in time to bribe the castle architect to plant, then negate, various traps, ending in the Master's 900 year imprisonment in the sewers of Tersurus. However, the Master ultimately recruited the Daleks to assist him.

The Doctor, realising that the Daleks planned to exterminate the Master once his usefulness was at an end, warned the Master of the danger through smells in the language of Tersuran. This was detected with the Daleks, and the Doctor was then killed by a Dalek energy beam. Emma was horrified until the Master said that the Doctor was in his ninth incarnation and would soon regenerate; sure enough, the Doctor then regenerated into his next body. (TV: The Curse of Fatal Death)

Behind the scenes

 * In PROSE: The Gallifrey Chronicles, there is a passing reference to the Doctor having "three ninth incarnations", which was intended to refer to
 * the Ninth Doctor played by Christopher Eccleston in the BBC Wales Doctor Who series;
 * this Ninth Doctor played by Rowan Atkinson; and
 * the Ninth Doctor played by Richard E Grant in the Scream of the Shalka webcast.
 * In the Instagram release of Russell T Davies' short story Doctor Who and the Time War, he liked a comment suggesting that, as the Ninth Doctor in that story was not explicitly identified, it could be any of the Doctor's ninth incarnations, including Rowan Atkinson's.