What age can teens drink wine?

[MollyHuaCha]

Sorry, I should know this (but I don't). We're going for DC's18th birthday dinner in a posh (and hopefully lovely) London restaurant. Can the younger teenagers drink a glass of wine at the meal?

[Olivialoves]

Must also add- it's on some venue's premises licences that they are not allowed to serve under 18's, so then they really aren't allowed to use discretion.