Originally Posted by stifle

What formally applies is a matter of BA policy, and that policy is that minors are not allowed alone into GC/GF. As has been pointed out on this board on a number of occasions, in the UK licensing law does not apply airside nor to complimentary provision of alcohol. If the passenger looks of age and doesn't make an issue of it, it's possible he may be admitted anyway (particularly if using TFW).