Emily Sheffield, sister of Cameron's wife, Alice, said she snapped a picture of Alice with a glass of champagne while the prime minister napped in the background of the shot prior to Emily's wedding two weeks ago near York, England, The Daily Telegraph reported Friday.
Sheffield, deputy editor at British Vogue, said she did not expect many people to see the picture when she uploaded it to social media site Instagram. However, it was soon shared thousands of times on Instagram and Twitter.
"Ok so I am the idiot today. For the record I had 8 followers when posted, all family and friends, then forgot to remove it #amateur," she said on her Twitter page.