THEY are as tireless as Cybermen, as dogged as K-9 and as indefatigable as a Sontaran attack squad.
In fact, Doctor Who fans are such a determined breed they have persuaded one of the world's biggest and most exclusive television festivals to open its doors to the public for a rare appearance by the man who reinvented the show.
The Edinburgh International Television Festival will, for the first time in its illustrious history, allow entry to non-broadcasting executives next month so they can listen to a masterclass by Russell T Davies, the writer of the show.
Even the eye-watering cost of attending the event – 500 for a three-day pass – will not deter Doctor Who fanatics from heading to Scotland from across the globe.
A spokeswoman for the festival said: "We are absolutely delighted that Russell has agreed to come to Edinburgh. Doctor Who has an extraordinary appeal and his appearance has generated a considerable amount of interest."
Because of this, people outside the broadcasting community will be able to attend, albeit at a cost.
"The festival is not selling tickets to Russell T's Masterclass. Members of the public can attend, but they would need to buy a pass for the three days," added the spokeswoman.
She said that, as things stand, there was no cap on the number of non-industry tickets being sold, but that might change depending on the extent of the interest.
Doctor Who super-fan Jason Lythgoe-Hay is among those planning to stump up the cash. He said: "It is perfect timing for me because I'll be up in Edinburgh that weekend for the Festival Fringe.
"In the past, I have paid to see Doctor Who stars at conventions and it would be great to see Russell speak."
Lythgoe-Hay, from Bolton, Greater Manchester, has created a life-sized Dalek model, which has gone on public display at Manchester's Museum of Science and Industry, and provided illustrations for the DVD release of the 1979 Tom Baker adventure 'City Of Death'.
Antony Wainer, spokesman for the Doctor Who Appreciation Society, said: "Russell is regarded as the man who saved Doctor Who and brought it back after 15 long years off screen.
"Will some fans be willing to pay 500 to see him speak about his time on the show? The answer is a definite yes."
Alexandra Looseley-Saul, who owns The Who Shop in London, also had no doubt that aficionados would snap up passes. "Totally die-hard fans will happily pay 500 to see Russell T Davies.
"It is a large sum of money, but that won't matter to the most dedicated Doctor Who fans. There will be a huge buzz about Russell's appearance in Edinburgh.
"He has that much of a fan base and Doctor Who lovers are desperate to hear what he has to say. The fans have an almost god-like admiration for Russell. They regard him as the person they have to thank for giving the series a wonderful new lease of life."
The festival is one of the most prestigious events in the television calendar, previously attracting speakers such as former US vice-president Al Gore and Jeremy Paxman.
Davies, the outgoing executive producer of the show, will give his hour-long masterclass at the Edinburgh International Conference Centre on Saturday, August 23.
The official programme states: "What's the next regeneration of Russell T Davies? Join him as he reveals his influences, his loves and hates about television and his plans for future projects."
The session will be chaired by Boyd Hilton, the TV editor of Heat magazine."
Douglas McNaughton, the deputy manager of the Edinburgh sci-fi toy shop Voga, said Davies' appearance would be a big draw.
"He is seen by fans as creating a miracle, by taking a show that was laughed off the screen in the 1980s and making it into the BBC's flagship drama.
"Davies has had an extraordinary career and has changed the face of television drama through shows such as Queer As Folk as well as Doctor Who."
McNaughton, a member of the Edinburgh Doctor Who Group, said Davies did not court attention.
"He does not do conventions or book signings. I think fans would like access to him so they can put their points of view about the programme across. What is interesting is that some Doctor Who fans confuse being a fan with actually owning the programme.
"For them, the version of the programme that goes on in their head is more real than the one that is on TV.
"They can have a very strong conviction that they know the characters perhaps better than the author himself. Russell is very careful about his public appearances and his contact with fans. I can see why he wouldn't necessarily want it to be an open forum."
Tomorrow, Davies is due to be given an honorary fellowship by Cardiff University.
His revival of Doctor Who in 2005 has proved to be a huge hit with viewers, with last weekend's climatic showdown with the Daleks being seen by more than 10 million viewers.
Davies was unavailable for comment.
Veteran Doctor Tom Baker set to return to the Tardis
Tom Baker could be set to turn back the clock and make a comeback on Doctor Who.
Reports claim that the veteran actor is being lined up to appear alongside David Tennant in the next series of the reborn show.
BBC bosses are believed to have held lengthy talks with Baker, who became an iconic figure when he played the Doctor in the 1970s and early Eighties (pictured below).
A BBC source claimed that it was a "certainty" that the 74-year-old would appear in the 2010 season.
The insider said: "The fans will love this. There have been great reactions when we brought back the Daleks, Davros and K-9, so can you imagine this?
"What hasn't been decided is what role Baker will play – The Doctor or another character."
Paisley-born writer Steven Moffat is taking over the BBC sci-fi classic from Russell T Davies.
Moffat is known to be a huge fan of Baker's boggle-eyed, eccentric incarnation of the time-traveller and it is understood that he is desperate to bring him back.
The revived series is taking a break in 2009, three special episodes aside, so Tennant can play Hamlet in a prestigious Royal Shakespeare Company adaptation.
Earlier this year Baker fuelled speculation of a comeback when he appeared at the opening of a Doctor Who exhibition in Earls Court, London.
Previously, the Liverpool-born actor had attempted to distance himself from his most famous role.
In 1983 Baker rejected the chance to appear in the 20th anniversary epic, The Five Doctors, which saw his predecessors Patrick Troughton and Jon Pertwee reprise their role alongside the then Doctor, Peter Davidson. BBC bosses used footage of Baker from an unshown episode.
Baker was unavailable for comment.