George Takei has mocked William Shatner's trip to space

George told the New York Post newspaper's Page Six column: "He's boldly going where other people have gone before. He's a guinea pig, 90 years old and it's important to find out what happens.

"So 90 years old is going to show a great deal more on the wear and tear on the human body, so he'll be a good specimen to study. Although he's not the fittest specimen of 90 years old, so he'll be a specimen that's unfit!"

Both George and William have previously admitted they exchanged cross words while working on 'Star Trek', which premiered in 1966, but the former 'I'm A Celebrity... Get Me Out Of Here!' contestant has insisted they don't have a genuine feud and it is only played on when his former co-star is looking for "a little publicity".

Speaking in 2015, George said: "It's not tension, it's all coming from Bill. Whenever he needs a little publicity for a project, he pumps up the so-called controversy between us.

"It's difficult working with someone who is not a team player. The rest of the cast all understand what makes a scene work – it's everybody contributing to it. But Bill is a wonderful actor, and he knows it, and he likes to have the camera on him all the time."

Earlier this week, William broke down in tears when the New Shepard NS-18 rocket he was travelling in landed back to earth.

He told Jeff: “I’m so filled with emotion about what just happened. It’s extraordinary, extraordinary. I hope I can maintain what I feel now. I don’t want to lose it. It’s so much larger than me and life.

“What you have given me is the most profound experience I can imagine. It hasn’t got anything to do with the little green men and the blue orb. It has to do with the enormity and the quickness and the suddenness of life and death.”

The crew made it up to an altitude of around 66 miles on the suborbital flight, and felt weightlessness.

But just a matter of minutes later, they began their descent and their capsule headed back down to Earth thanks to three parachutes.

The crew touched down in the desert at a speed of around 15mph.