LHR T3 was a zoo yesterday (the day after AA and IB moved back to T3). There is one single line to get up to security. All access from check-in up to security was roped off and guarded, except one.That one line stretched through the width of the terminal and outside past the courtyard. Once upstairs, the line branches into regular and Pre-Check as before, but there is no distinction downstairs and upstairs until the branch. Flagship First Check-In and Five Star are forbidden from escorting anyone to the front of the security line unless they are in imminent danger of mosing their flight, maximum one hour before departure. They were able to escort people upstairs to the end of the Fast Track line.