A boy carries a lion soft-toy on London's Whitecomb Street.
A boy carries a lion soft-toy on London's Whitecomb Street late on November 4, 2004. The nightmare before Christmas has officially started, according to a mathematician who claims to have calculated the moment fun in festive shopping turns into a headache. The precise time the pleasures of present buying were outweighed by the stress and irritants, was 12.30pm on a so-called Black Saturday, according to Dr Tony Mann, the head of mathematics at Greenwich University, London. REUTERS/Pawel Kopczynski PK/GB