Originally Posted by
YVR Cockroach
As far as liquid duty free goes, as long as it is acquired onboard an E.U. carrier or at an E.U. airport andis in a sealed (by carrier or duty-free shop) E.U.-approved bag, it can pass through security in the U.K. (or elsewhere in the E.U.) as long as it is within 24 hours of purchase. The receipt is generally put inside this sealed bag.
Yes, this is how the rule works. The important part is that your purchases are sealed in a tamper-proof bag, and that the bag has not been opened.