Rachel Riley is set to take a break from Channel 4's Countdown and her replacement has already been confirmed. 

Oxford and Cambridge university mathematician Dr Tom Crawford will be stepping in as the game show's number expert. 

Rachel, 39, is taking a temporary step away from her role on Countdown while she works on another project. 

The show sees contestants tackle linguistic and mathematical challenges while the clock ticks. 

It first aired in 1982 and is currently hosted by radio presenter and TV star Colin Murray, 47. Susie Dent, 60, also features as the show's lexicographer.

Very qualified for the new role, Dr Crawford has a PhD in Fluid Dynamics from the University of Cambridge and completed a maths degree at the University of Oxford.

He has over 200,000 subscribers on his YouTube account, Tom Rocks Maths and 22,000 followers on Instagram.

Some of his videos have racked up millions of views and he regularly posts clips of himself tackling exams or discussing math-related topics.

Dr Crawford posted a photo of himself outside of a dressing room on Instagram yesterday with the caption: 'Prepare for the most ridiculous announcement coming tomorrow... any guesses as to which TV show I’ll be on? #tomrocksmaths #TVdebut #TVshow.'

The maths boffin is a Fellow by Special Election at Oxford's St Edmund Hall and is a Public Engagement Lead at the university's department for Continuing Education, according to his website.

He also teachers Applied Mathematics at Robinson College.

Rachel has featured on the show since 2009, while Colin joined in 2022 after taking over from Anne Robinson, 80.

Countdown has seen plenty of memorable moments over the years, including just last month when host Rachel was left red-faced as she was forced to spell out a rude seven-letter word by her countdown co-star Susie.

At the end of one of the rounds, host Colin was keen to find out how long contestants Joe and Anne's words were.

But unfortunately they didn't manage to find one over four.   

Joe explained that he found alas, while Anne pointed out the word lose.  

Presenter Colin then went over to Dictionary Corner, where guest Nicki Chapman, 58, shared some good news with lexicographer Susie. 

Nicki said: 'Tough, really tough. But Susie has come up with arousal for seven.' 

An impressed Colin replied: 'Wow. Sensational, well done Susie, well done.' 

The camera than panned back at Rachel who looked very awkward after finding out Susie's racy word.

The TV star then spelt out her word on the board. 

Countdown airs weekdays on Channel 4 and is available to stream on channel4.com.