Eccleston's incarnation of the Doctor is a war-torn loner who is more pragmatic and less eccentric than his previous selves, fiercely determined to protect the innocent at all costs, and prone to using humour to mask the trauma he suffers from as a result of the Time War.

The Doctor and Rose also briefly travel with Adam Mitchell (Bruno Langley) and are later joined by Captain Jack Harkness (John Barrowman), a reformed con man from the 51st century.

The Doctor, Rose, and Jack form a close team but are separated in the series finale in which each character has to make difficult choices and face sacrifice.

[9] In "Boom Town", when the Doctor encounters Blon (Annette Badland), the only Slitheen to survive the Downing Street explosion, in present-day Cardiff he has doubts over whether or not to send her home to be executed.

The regeneration scene is cut short just before a CGI rendition of Eccleston's likeness can be fully seen, as he declined to return for the episode and showrunner Steven Moffat wished to honour his decision.

Released on the 7 October 2021, "The Ashes of Eternity" was an exclusive-to-audio story from BBC Audio in collaboration with Penguin Books featuring the Ninth Doctor and Rose.

In the final episode, he rescues a young blind man named Callen (Adam Martyn) and his talking guide dog Doyle (Harki Bhambra), taking them away in the TARDIS to find a new home.

[29] The third series opens Martyn and Bhambra reprising their roles, implying that Callen and Doyle have become temporary companions as the Doctor mentions having taken them on several adventures in the interim.

In the final volume of series three, Alex Kingston joins the main cast of The Ninth Doctor Adventures, reprising her role as River Song for all three episodes.

[33] "The Big Finish experience has, to date, been enjoyable and has afforded me the chance to revisit a character I was able to bring to life almost twenty years ago.

[37][38] However, following the September 2003 announcement that the series would return to television with a new actor in the title role, the canonical status of the so-called "Shalka Doctor" was left in doubt.

[39] Eccleston cited the quality of the scripts as a reason for joining the cast, stating in an interview on BBC's Breakfast programme that he was "excited" about working with Davies.

[46][47] In March 2013 a source for the BBC indicated that Eccleston had discussed plans for Doctor Who's 50th anniversary special, which aired in November 2013, with Davies' successor as executive producer, Steven Moffat.

Remarking on this aspect of his characterisation, Eccleston stated that the character is "a scientist and an intellectual, and a lot of people seem to think you can only be those things if you speak with Received Pronunciation which, of course, is rubbish".

[51] Eccleston felt that his Doctor lives solely for the present, avoids thinking about his painful past, and that his only view of the future is simply that "it's there".

[53] However, he also drew out differences between the Doctor and traditional children's heroes, describing the character as "brutal at times [...] confrontational [...] inflexible" and that he "sometimes creates carnage [...] there's nobody like him in Disney".

Matthew Sweet of The Evening Standard highlighted the dichotomy of the character being "brave and wise and brilliant" but also "rough and ready" and "down-to-earth".

[54] A loose story arc that informed the Ninth Doctor's characterisation during his tenure is his opinion on the destruction of his own race, the Time Lords, which occurred offscreen before episode one.

[55] Davies remarked that the Ninth Doctor carries a lot of survivor guilt, which is why he "strides through the universe wearing a dark leather peacoat saying 'don't touch me'".

Davies felt it was important to take the Doctor away from mythological offstage concepts such as the Time War and provide a conclusion that focused on the relationship between the character and Rose.

The character was first conceived during Russell T Davies' 2003 pitch to the BBC: it was always the intention for Adam to join the TARDIS team after Rose developed a liking for him.

[63] John Barrowman, reflecting on the interrelationships between The Doctor, Jack and Rose, felt that "the subtle sexual chemistry between all three characters... was always in play" with the caveat that "the relationships were by no means driven by desire".

[64] SFX magazine also commented on the "intoxicatingly flirtatious dynamic" and compared the trio to "a Buffy-style Scooby gang who can quip in the face of danger".

He felt that the "brusque, sarky and virile" Ninth Doctor "transports us back to the golden era of Jon Pertwee when the series still had that edge of darkness.

"[67] Marena Manzoufas, head of ABC programming, commented after picking up the series that Eccleston "has brought a new dynamic energy to the role" and the show would appeal to both long time viewers and new fans.

[69] Richard Henley Davis of The Economic Voice also notes that Tennant "had big boots to fill after Christopher Eccleston's Doctor Who, which many believe to be the greatest incarnation of the lunatic time lord.

He comments that in online fandom there was a sense "of a ship being steered in a different direction" and praises the plot device of the Time War as allowing the character to become mysterious again by providing him a "blank slate".

Blair ends his retrospective by noting that without the foundations laid by Eccleston the show "wouldn't have been able to move onwards towards the even more popular David Tennant era".

"[72] Ahead of the series premiere on Australian Network ABC the Sydney Morning Herald's Robin Oliver predicted that older viewers "will find Eccleston easily the best time lord since Tom Baker.

"[83] Gavin Fuller of The Daily Telegraph named him the ninth best Doctor, noting that Eccleston was "a serious actor" and "his attempts at a lighter style could seem a tad forced", though this was "offset by his showdowns against the Daleks".