Rachel made her television debut in 2009 when she took over from Carol Vorderman as the numbers expert on Countdown. Rachel studied maths at Oxford University and before entering the world of television she was a data analyst.
Riley was encouraged to apply for the Countdown position by her mother. She did not have an ambition to be a television presenter, but decided to apply because she was interested in the numbers part of the game.
Riley was chosen from more than a thousand applicants despite having no television experience. In an article for BBC News, she stated, ‘There’s only one cool maths job around and I was lucky enough to get it so I’m absolutely thrilled’.She began presenting Countdown alongside Jeff Stelling from 12 January 2009. In an interview in August 2009 she revealed that it had been difficult for her to step into Vorderman’s shoes.
Rachel also does the letters and numbers round on Countdown on Channel 4 ,The 8 Out of 10 Cats Does Countdown series.
She also appeared on Strictly Come Dancing on BBC 1.
It was recently announced in April 2014 that Rachel has left the show , to be replaced by Amy Williams later in the year