Well, fans of Doctor Who are in certainly high spirits, as the iconic sci-fi series of the same name has just celebrated its 50th anniversary. Thanks to the time-traveling TARDIS, the Doctor and his companions have taken us to ancient Rome as well as future worlds. Now, fans across the world are celebrating the universe’s most famous Doctor.

In London, fans gather at the ExCeL Exhibition and Convention Centre for an official celebration featuring old and new Doctors, including Matt Smith, Sylvester McCoy, Peter Davison and Colin Baker.

The event kicks off a weekend of "Doctor Who" related festivities. Fans get a chance to see demonstrations, monsters, stunts, workshops and purchase official merchandise.

"There’s Britishness, there’s science, there’s education, there’s bringing families together and there’s an enduring sort of mystic-ness (sic) to it all.

"Well it just goes back to my childhood. I remember my brother scaring the bejesus out of me with the ’Pyramids of Mars’ going around as one of those mummies, just scaring the you-know-what out of me and it just endures; the charm of the Doctor. It’s just brilliant. It’s not in your face, it’s not preachy, it’s just great fun."

A character who began life as a crotchety older man played by William Hartnell, is currently a cheery young charmer in a bow tie played by 31-year-old Matt Smith.

According to Matt Smith, the current doctor, the show’s appeal has a lot to do with its concept.

Matt Smith, Actor of "Doctor Who", said, "The fact that it’s a show that explores time travel and can go anywhere in space and time and you have a character that can change and regenerate and there’s something timeless about those ideas and here we are 50 years later."

One of the secrets of its longevity is that The Doctor can regenerate into a new body when the old one wears out, allowing the show to outlive any individual star.

The anniversary episode "The Day of the Doctor" was written by Steven Moffat, who’s been the show’s executive producer since 2009. He’s also writer of the hit TV series "Sherlock".

Steven Moffat, Writer/Producer, said, "The fact that ’Doctor Who’ can simultaneously be a grand old tradition and a brand new show and can address each generation directly, not as a misty ancient figure that your big brother likes or your big sister likes or your mum likes but as your show, your doctor can be there, so that I think is why. It literally regenerates itself."

"The Day of the Doctor" offers a rare chance to see multiple Doctors onscreen at the same time.

11th doctor Matt Smith teams up with his predecessor David Tennant, while John Hurt plays a hitherto unknown, darker incarnation of the character.

Smith will soon hand over The Doctor’s trusty sonic screwdriver as he regenerates in the latest episode.

Meanwhile a 12th Doctor, played by Scottish actor Peter Capaldi, is due to make his entrance during this year’s Christmas Day episode.