Countdown star Rachel Riley and actress Ashley Jensen have teamed up with Alzheimer's Research UK to launch The Mighty Quiz, taking place nationwide on April 27, to raise money for the charity.

Riley has created eight Facebook videos to encourage people to 'defeat dementia' by getting together to 'tackle trivia, crack conundrums and face physical feats', and commented 'I love putting my brain through its paces, so I can't think of a better way to raise money for Alzheimer's Research UK. Whether trying to name that tune or sculpt a masterpiece from foil, The Mighty Quiz is a great excuse to get your friends together to tackle trivia and put your senses to the test. We need Mighty quizmasters across the nation to get their packs and get organising'.