This video shows the heart-warming moment when a shop security guard burst into a duet with a customer - in perfect pitch. Keith Davis, broke into his feel-good rendition of Elvis Presley's 'The Wonder of You' alongside shopper Mandy Allport. The spontaneous sing-along was captured on camera by 54-year-old Mandy's work pal, Sharon Hanna, at her local Sainsbury's. The pair have since become a viral hit sensation, with more customers asking Keith if he can sing them a song.