After paying $28 million to go into space with Jeff Bezos a mystery would-be astronaut then decided they had something better to do.

Mr Bezos, the richest man on Earth, will be on his company Blue Origin’s inaugural space tourism flight on July 20.

He had auctioned off one of the three other seats but, in an extraordinary twist, the winner has backed out citing "scheduling conflicts."

The unidentified millionaire will fly on a future Blue Origin mission after they have dealt with whatever conflict it is they have next week.

Instead, Mr Bezos will be accompanied by Oliver Daemen, 18, a physics student, who will become the youngest astronaut ever.

Oliver Daemen, 18, from the Netherlands is about to become the youngest person in space.

Credit: Daemen family

The other two seats will be filled by the Amazon’ founder’s brother Mark, and Wally Funk, 82, a veteran female pilot who will become the oldest person in space.

Mr Daemen’s father, Joes Daemen, is chief executive of a Dutch private equity firm.

The elder Mr Daemen took part in the auction and secured a spot on the second flight

He "paid for the seat and chose to fly Oliver," Blue Origin said. The company declined to say how much was paid.

When the auction winner dropped out the teenager was moved up to the first flight.

The $28 million is being donated to Blue Origin’s charitable foundation Club for the Future.

Bob Smith, Blue Origin’s chief executive, said: "The winner of Blue Origin’s auction, who has asked to remain anonymous at this time, has chosen to fly on a future mission due to scheduling conflicts.

"We thank the auction winner for their generous support of Club for the Future and are honoured to welcome Oliver to fly with us."

He added: "This marks the beginning of commercial operations and Oliver represents a new generation of people who will help us build a road to space.”

Mr Daemen graduated from high school last year and holds a private pilot’s licence.

An illustration of the capsule that will be used to take tourists into space

Credit: Blue Origin

The trip will be a lifelong dream for the teenager who has been fascinated by space, the moon, and rockets since he was four-years-old, Blue Origin said.

He plans to attend the University of Utrecht in the Netherlands to study physics and innovation management in September.

Mr Bezos has been locked in a race with billionaire rivals Sir Richard Branson and Elon Musk as they seek to usher in a new era of commercial space travel.

Mr Bezos will blast off from West Texas for a 10-minute flight.

Last week, Sir Richard was on Virgin Galactic’s rocket plane when it took off from New Mexico.

He flew above the 50-mile altitude considered qualification for astronaut wings.

Mr Bezos will go higher, passing the 62-mile high Karman line considered the boundary between the atmosphere and space.