Astronaut Tim Peake has told how he thought he had seen UFOs while in space, only to discover it was in fact droplets of liquid leaking out of a Russian probe vehicle.

Major Peake became the first official British astronaut to join the International Space Station crew in 2015, and during his mission he earned a Guinness World Record for the fastest marathon in orbit.

Major Peake, who spent six months in space, told The Graham Norton Show: “Space is very black and one day I was looking out and there were three lights moving in formation and then there was a fourth.

Graham Norton Show – London
Tim Peake recalled a moment in space when he thought he had seen a UFO (Matt Crossick/PA)

“We were perplexed, until we realised that what we thought were the far away lights of alien spaceships were actually very close small droplets.

“What was happening was liquid leaking out of a Russian probe vehicle, crystallising instantly and reflecting the light. What we were seeing was Russian urine.”

The astronaut, who has released his autobiography Limitless, appeared on the programme alongside Gary Barlow, Nadiya Hussain, Richard Osman and Mariah Carey – who joined from the US virtually.

Major Peake said Limitless is “really the journey from young boy to astronaut”, adding: “I feel a bit of a fraud because as a boy I had no ambitions at all of wanting to be an astronaut – I was obsessed with being a pilot.”

Asked by Take That star Barlow if he was scared going into space, Major Peake said: “There is always a thought at the back of my mind that I am rolling the dice, but the overriding feeling is of adrenalin-fuelled excitement.

“Walking in space feels incredibly exposed and the danger is palpable out there.”

Graham Norton Show – London
Bake Off winner Nadiya Hussain also appears on the Graham Norton Show (Matt Crossick/PA)

He was also asked if he hopes to return to space.

“I’d love to – absolutely. In fact, we are all slated for a second mission between now and 2024. I’m waiting by the phone,” he said.

Meanwhile, Hussain, who won the Great British Bake Off in 2015, said the Channel 4 show’s latest victor Peter Sawkins is “in for quite a ride”.

Sawkins, a 20-year-old accounting and finance student from Edinburgh dubbed the “baby-faced assassin”, is the show’s youngest ever winner.

Hussain told Norton: “It is such a bizarre experience because there is a naivety to filming something like that because you are so immersed and focused on baking you forget that there are millions of people watching you.

“You walk out and you think, ‘How do they know me?’ But he will love it. It’s great.”

She also spoke about her new book and BBC TV series, Nadiya Bakes, saying: “It was important to me after Bake Off to cement myself in a kitchen where I am happiest, and when I wrote my first book it was all about cookery.

“A baking book has been a long time coming, and it’s one of the best things I have ever done because five years later, it feels really important to me to do a baking book and feel I am comfortable in my industry now.”

The Graham Norton Show airs on BBC One on Friday at 10.45pm and is also available on BBC iPlayer.