A Who Wants to Be a Millionaire contestant lost out on a major prize following a difficult question that even host Jeremy Clarkson admitted he would have struggled to answer.

Contestant Jen had made an impressive run on the show, reaching £500,000 ($A943,000), before facing a crucial question that would determine whether she could double her winnings.

Clarkson asked: “According to Guinness World Records, which of these have travelled at over 260 miles per hour during a competitive game or match?”

The options were: “A. Tennis Ball B. Ice Hockey Puck C. Badminton Shuttlecock or D. Table Tennis Ball.”

Unsure of the answer, Jen chose to use her Phone A Friend lifeline, calling her father Chris, however, he was also unable to help.

With no lifelines remaining, she was faced with a difficult decision to walk away with £250,000 ($A472,000) or attempt the question for a chance at £500,000.

Jen decided to take the risk, guessing the answer was an ice hockey puck, which was unfortunately incorrect.

As a result, she dropped back to her safety net of £64,000 ($A120,000), meaning she lost out on £436,000 ($A823,000) in potential winnings.

The correct answer was Badminton Shuttlecock.

The question proved just as challenging for viewers at home, with many taking to social media to share their confusion.

“Still staggered at this £500,000 question,” one person wrote.

“I’d have been all in on ice puck and shown to be clueless”.

Clarkson himself responded to the comment, writing: “Me too”.

“If it’s any consolation, I’d have said hockey puck too,” another viewer added.

Image: ITV