Yesterday -
EDI. Group 0, then group 1

LHR. Staff person at the start of the tensator barrier shouting "group 0 and group 1"....start checking boarding cards and ID... first few start going though the gates. Then someone on the tannoy "Group 0 only please, that's group 0 ONLY"
two seconds later, "and Group 1"

Quite a complex process, understand the difficulty adapting to the change.