As Christopher Eccleston makes his long-awaited return to Doctor Who, speculation begins regarding a possible "Five Doctors" 60th anniversary special - could it happen? When Doctor Who returned to screens in 2005, respected Mancunian actor Christopher Eccleston was cast as the Ninth Doctor, and while he would only stay a single season, it's no overstatement to say Eccleston was instrumental in bringing The Doctor back for a modern audience. Unfortunately, the departure was acrimonious, with Eccleston citing the BBC show's leadership as a key factor in his decision to leave. These issues have prevented Eccleston from any further involvement in Doctor Who, including turning down a part in the 50th anniversary special "The Day of the Doctor."

Last week, a shockwave was sent through the time vortex when Big Finish announced a series of Ninth Doctor audio adventures starring Christopher Eccleston as The Doctor once again, marking the actor's return to the franchise after a lengthy absence. Despite the problems that led to his regeneration (feuds with producers, not absorbing TARDIS energy from Rose Tyler), Eccleston has always spoken positively about playing the Ninth Doctor. Moreover, the actor recently started making convention appearances, and he describes the process of meeting Doctor Who fans and engaging in that world again as a healing one, likely contributing to his Big Finish arrival. Perhaps also worth noting is that working with the Big Finish team will be an entirely different experience to filming the first season of Doctor Who with Russel T Davies.

Related: Doctor Who Theory: Why The Doctor's Age Always Changes

The Ninth Doctor's return was widely celebrated among the Doctor Who faithful, but while the sensible thing would be to simply enjoy Eccleston's return in the present, it's hard not to think a few steps ahead. After all, what's Doctor Who without a reckless leap into the future? Doctor Who's big anniversaries are usually celebrated with multi-Doctor stories - 1972's "The Three Doctors," 1983's "The Five Doctors," 2013's "The Day of the Doctor." The BBC show's 60th anniversary arrives in 2023, and the prospect of a modern version of "The Five Doctors" is already proving too tantalizing too ignore. David Tennant, Matt Smith, Peter Capaldi, Jodie Whittaker and Christopher Eccleston - all five modern incarnations of The Doctor in one celebratory epic.

Christopher Eccleston and Rose Tyler played by Billie Piper in Doctor Who stand in front of a Tardis and look up.

Of course, there are still some obstacles to overcome. There's a huge difference between Eccleston returning in audio form and on screen, and this might be a jump the actor doesn't wish to make. Even if all five actors were willing to return, scheduling filming between all of them would be a logistical nightmare, especially if companions were thrown into the mix too. After "The Day of the Doctor,"  the BBC might not even mark Doctor Who's next big milestone with a multi-Doctor story, instead preferring to try something new like a live episode or a feature-length movie.

Even so, there's a sense that stars are beginning to align ahead of Doctor Who's 60th anniversary, especially with Eccleston's return. As highlighted by the original "The Five Doctors" episode, a quintet of Time Lords pushes the limit of how many protagonists can be crammed into a single adventure. This means the 60th anniversary will be the only opportunity all of the modern Doctors can realistically appear together in a single episode. By the time the franchise's 70th birthday rolls around, there would be far too many actors to accommodate. Speaking of future Doctors, 2023 might also coincide nicely with Jodie Whittaker's regeneration, which could be a fitting final scene for a 60th anniversary "Five Doctors" special. Given the excitement that followed the return of just Eccleston's voice as the Ninth Doctor, the reaction would be huge if he announced a TV appearance in the coming years.

More: How Doctor Who's 50th Anniversary Would've Been Different With Christopher Eccleston

Doctor Who returns this Christmas with "Revolution of the Daleks" on BBC.