The world's largest Star Trek convention is taking place as the franchise celebrates its 50th anniversary this year.

Fans of the iconic show have descended on Birmingham to meet the cast and crew from several shows.

'Destination Star Trek Europe' got off to a rousing start at the NEC in Birmingham in the UK Friday.

Organisers say thousands of fans, many dressed in costumes, gathered from all over the globe.

William Shatner, who played the original Captain James T Kirk, was asked if 50 years on he would change anything about it.

"The reality is we're here as part of a celebration of 50 years of Star Trek. It's a showbiz phenomenon. Fifty years ago, the Star Trek went on the air. And 50 years later, a lifetime later, we're still talking about it.

"But here this magical show had enough magic to it to entice you to come here and talk to me 50 years later. What could you...? How could you -- me -- be so callow as to think you could change something? So, no, I would not change anything. That might interfere with its longevity."

William Shatner on stage | Image: startrek.com

Walter Koenig, who played Chekov, explained that conventions never, ever get old for him.

"It never gets old," he said, "because I have such an extraordinary ego that I soak this in.

"I lap it up. I flew 10 hours from LA just so I could hear you guys applaud."

Walter Koenig | Image: startrek.com

George Takei, who played Sulu, marveled at the generations of Trek fans he meets.

He says he sees parents with their kids, grandparents with the their grandchildren. "You have," he joked, "multiplied like Tribbles."

Before leaving the stage, Takei was presented by Craig Glenday of the Guinness Book of World Records with a framed citation declaring Trek "the most successful TV sci-fi franchise."

George Takei (left) with Craig Glenday of the Guinness Book of World Records | Image: startrek.com

British actress Marina Sirtis, who played Troi on 'The Next Generation', declared "My people!!" as she took to the stage.

Asked to comment on Trek's 50th anniversary, she cracked: "Forget 50 years. Our TNG 30th anniversary is coming up next year. That's more important!".

Marina Sirtis | Image: startrek.com

After speaking to the press, the actors walked over to the orignal Enterprise bridge set for an epic photo.

Shatner settled into the captain's chair, with George Takei and Walter Koenig at the helm, surrounded by everyone from Marina Sirtis, Connor Trinneer, Jeffrey Combs and Chase Masterson to Terry Farrell, Alice Krige, Eric Pierpoint, Eddie Paskey and others.

"Everybody realized they'd just witnessed something not only special, but quite possibly never to happen again", organisers say.

Cast members from several shows unite | Image: startrek.com

Among others attending are Adam Nimoy, son of Spock actor Leonard Nimoy, who died in 2015.

Adam Nimoy | Image: startrek.com

As lines queued for the Star Trek actor photo ops and autographs, many fans - and some celebrities - took advantage of the other photo ops, including 'The Next Generation' and 'The Original Series' bridge sets, a Klingon captain's chair, a Borg regeneration chamber and a transporter.

While a Prop and Costume Museum features screen-used items such as Data's head, assorted rifles and disruptors, and also Janeway, Neelix, O'Brien and Quark costumes.

A 'Red Shirt Fight Off' also welcomed fans to come up on stage, get clobbered with a rock by a Gorn alien and to die a righteous death.

A young girl named Beth and her father won Friday's event: