Codenamed "Merchandise 7X", the list of ingredients that go into Coke - 922 million litres of which were drunk in the UK last year - has been kept carefully shrouded in mystery since the drink's inventor, a medicinal chemist called John Pemberton, first wrote it down in 1886. These days it is supposedly kept under 24-hour guard in a vault in Atlanta, Georgia, which is odd considering that author M