SEATED beside his director JJ Abrams, Benedict Cumberbatch delighted assembled press at this morning’s first Star Trek Into Darkness press conference in City Hall at Tower Bridge.

Ahead of tonight’s premiere, the 36 year-old actor – who was this week voted Britain’s Sexiest Man for the second year by The Sun – even received a small round of applause after he embarrassedly rattled off the details of the training regime – “chicken, chicken, chicken” - he followed to achieve the necessary physique for the role of the movie’s baddie John Harrison.

"That was the hardest thing in all honesty because it meant an awful lot of eating and a lot of working out in a very short space of time," he explains.

"But fortunately, I had a fantastic trainer in the shape of Mr (Patrick) P-Nut Munroe, who also trained Mr Tom Hardy. It was a lot of work and yet I really enjoyed it.

"I've never been asked to before, and it was integral to the character, who had to have a strong physical shape and presence and be able to move at the same time so I had to be able to stretch and fling my arms and legs about a bit."

"I didn't go the junk food way. For two weeks I was eating chicken, potatoes and broccoli. And protein shakes. There was one stage where I ate about 4,000 calories a day and it's horrible."

Benedict admitted that he’d hadn't realised that the other actors on the film had dieticians to help them bulk up, “so I said, ‘Can I have a dietician?’ And they said ‘yes’.”

And he expressed a new-found sympathy for the members of the fairer sex, admitting: “I turned into a creature from hell. Now I know how girls feel. Diets are sh*te.”

He also let everyone in on what turned out to be one of big issues, laughing: “Which way to do my hair was the hardest thing really - straight or curly, or long with bangs, or a sort of ponytail, or maybe no hair!"

In JJ Abrams’ follow-up to the phenomenally successful reboot of the Star Trek franchise in 2009, Benedict joins, among others, returnees Chris Pine as James T Kirk, Zachary Quinto as Spock, Zoe Saldana as Uhura, Karl Urban as Dr Leonard ‘Bones’ McCoy and Simon Pegg as Scotty.

His role is a crucial one, clouded in necessary secrecy to prevent fans’ fun being ruined when they see the film for themselves, but it’s safe to say it’s his most action-orientated performance so far and he’s the best thing in the whole shebang.

The nuances and complexity of his interpretation are typical of the brilliance that has ensured his fanbase has grown exponentially the more fans are allowed to witness his abilities. Whether it be the BBC’s Sherlock – currently filming series three (“I was playing Sherlock until midnight so my powers of deduction are a bit sleepy this morning”) – voicing Smaug in The Hobbit or on stage in Danny Boyle’s immense Frankenstein, Benedict seems always to be on his best game, something JJ Abrams was counting on.   

Abrams, the creator of Felicity, Alias and Lost, and the man who will also direct the next Star Wars film, revealed: “He came to the table with a whole new attitude, personality, background and strength. But he’s such a compelling and powerful character that it works.

“He has a wry sophistication to his approach that is so right. It was the right way to go because he was so damn good. I am grateful to the (Star Trek) writers, most notably Damon, who said, ‘you should check out Sherlock’. And it was the perfect medicine for what we were suffering from [the struggle to cast the Harrison role].

“Benedict famously auditioned on an iPhone and it was clear we’d found our man. Working with Benedict exceeded all our expectations - everyone stood a little bit taller when he was around.”

JJ wanted him, but it took Mr C a while to realise.

Benedict recalled: "I got an email and I didn't pick up on the signals. The email said, 'Do you want to come and play?' and I thought, 'What - squash or tennis or some kind of racquet-based activity?' Then the penny slowly dropped.

"It was the most thrilling news. I was a huge, huge fan of the first film. It's just such a rich experience to be in his and the storyteller's hands on a journey of high emotion, adventure, romance and comedy. I knew it would be a riot so I was well over the moon."

Chris Pine was impressed by his abilities: “Benedict went at this character like a scalpel. His performance is so precise, I watched in awe as a fan and a fellow actor. It was chilling and creepy and hands down I think he has created some moments that will stand in the pantheon of great Star Trek moments.”

Co-star Karl Urban adds: “I loved watching Chris and Benedict when they were doing scenes together because the sparks would literally fly.”

The Harrow-educated bachelor admits that he admires Harrison’s “sense of honour to his own, protecting your own tribe.

“JJ and I talked a lot about my character about who is this man and what role has he played in Starfleet. He has a moral core - he just has a method which is pretty brutal. One man's terrorist is another man's freedom fighter.

“It was there in the script and to me it was a beautiful thing to be able to play somebody on a mission of revenge trying to bring about what he sees as justice and a change in the order. You oscillate between abhorring him and feeling something for him.”

Whatever the film’s box office or critical reception, his portrayal of Harrison is surely yet another memorable milestone in what has already been a remarkable career.

How does he approach each new, ever more daunting, challenge, especially when taking on a role which has been made famous by other actors in the past? Does he go out of his way to avoid, for example, internet buzz?

“I always avoid going on the Internet. A lot of trust goes to [the creative teams of each project], whether it's Mark and Steven doing Sherlock. It’s done with such authenticity and respect for the canon and that does the heavy lifting for you.

“I try to trick myself into believing that no one has ever gone there before.”

Given the dream projects he has already completed, more of which are surely to come, what would his ten year-old self have said if he’d known what lay in his glittering future?

“Gosh how you've grown… I don’t know. He’d have been pretty chuffed. I think. I was probably playing Ann in Half A Sixpence at school at that time so being in Star Trek was probably far from Ann's mind.

“He wouldn't have quite believed it. And he still doesn't.”

Star Trek Into Darkness goes on general release in the UK next week.