Doctor Who: Who is the longest-serving Doctor, really?

Some Doctors last years, some weeks – but recently, we’ve found ourselves pondering an apparently obvious question. Which actor, technically, properly, was the Doctor for longest?

Immediately, fans will be chiming in with the "real" answer – national treasure and Fourth Doctor Tom Baker, who appeared in the role from 1974-1981 (aka just under seven years), around three years longer than any other Time Lord (David Tennant comes second with around four and a half years).

But was he actually the Doctor for the longest? What of Sylvester McCoy, who while only playing the Doctor on TV for a little over two years, only regenerated in 1996, technically meaning his reign lasted for nearly nine years, a good couple longer than Baker held the role?

And what of Paul McGann? While technically playing the Doctor for just one night in 1996, McGann was sort of the incumbent Doctor until 2005, when Christopher Eccleston took over the role – once again, nine years – with the Eighth Doctor regularly appearing in comics, spin-off novels and (played by McGann) audio dramas, definitely keeping the character alive during Who’s years in the wilderness.

Or could we count McGann's era as lasting even longer? After all, his last appearance as the Doctor and regeneration – seen in 2013 mini-episode The Night of the Doctor – "counts" as him playing the character on-screen, albeit not continuously. Including that, could we say he played the Doctor for 17 years? And then, can we add three years to David Tennant’s count considering he played the Tenth Doctor again the same year?

And what of spin-off media? In Big Finish stories, books and Time Lord Victorious tie-ins, McGann’s Doctor still lives on to this day – though for that matter, so does Tom Baker’s Doctor. By that logic, has Tom Baker been master of the TARDIS for 46 years?

As with any discussion trying to break down the twisted, complicated world of Doctor Who into hard data, the answer is… confusing. Baker is the longest-serving Doctor… but of course McCoy counts… but who could discount the years Paul McGann spent playing his Time Lord? It’s enough to make your head spin more than tracking the Morbius Doctors and series 6B.

Even a Doctor like Christopher Eccleston, who has definitively only played the Doctor for just under three months and not returned to the same role since, is sort of still the Doctor. Eccleston has attended conventions to talk about Doctor Who and recorded video messages in character for fans, while the Ninth Doctor continues to appear in audio dramas (just not voiced by Eccleston) and books.

Maybe the simple answer is, then, that there isn’t a simple answer. Could we just count on-screen hours in the role? Possibly – but it seems unfair to cast aside McGann’s years of audio adventures. Could we just count the years the actor spent on-screen as the "main" Doctor? Possibly again – but it’s hard to argue that Sylvester McCoy’s Doctor doesn’t "count" in the TV movie, if we count years like 2016 and 2019 where the TV show wasn't really on air.

Like the Doctor’s life in-series, the actors who play the Doctor overlap, crossover and often meet, and it’s difficult to lay it all out in simple, numerical terms – no matter how much Whovians and, er, online articles might try to. Who knows? Maybe you actually have to be a Time Lord to work it all out...

Doctor Who: Revolution of the Daleks comes to BBC One in late 2020/early 2021 – check out what else is on with our TV Guide