BBC Breakfast favourite Dan Walker, 43, has apologised to his 657,000 Twitter followers after making an “unbelievable” spelling error.The journalist was alerted to his mistake by fans when he shared a surprising encounter with darts world champion John ‘Boy’ Walton in his local shop.Dan shared a socially distanced selfie with the former sportsman and wrote: “What a treat to bump into 2001 darts World Champion John ‘Boy’ Walton - who is working at our local @coop_food in Sheffield. “Lovely chat in the home baking and canned fish isle #CottonEyeJoe #Arrars @BDOdarts @OfficialPDC.”(sic)Unfortunately, in all the excitement, Dan failed to realise he had spelt the word “aisle” incorrectly in his post.Journalist Hamish Arnold pointed out the error.