This charity single is sung by the Military Wives Choir, the wives and girlfriends of British servicemen fighting in Afghanistan who were brought together by choirmaster Gareth Malone for the BBC2 series “The Choir.” Having sold 556,000 copies in just over a week, the song has become a phenomenon — the fastest-selling single since 2008, outselling the rest of the Top 20 combined.

“Wherever You Are” is composed from letters between these wives and their men — Britain’s heroes — as they served on the battlefield.