According to the Heathrow Airport website, I see that the liquid rules have changed for Terminals 2, 3, and 5 to allow liquid containers up to 2 liters. Terminal 4 is in the middle of installing the new scanners, so some lanes still go by the old 100 ml rules. Good news! Britain's airports have long been more strict on liquids than even many European/North American airports, so it's nice to see that there is progress on the horizon. Ominous signs for the rest of Europe, I'd imagine, given the number of EU airports making similar moves.
Source: https://www.heathrow.com/at-the-airport/security-and-baggage/hand-baggage-and-liquids