Yesterday I went to Heathrow airport and took the wrong lane and ended up on the ramp to the drop-off area at T2 at which point I had no option but to continue. I didn't want to be there and wanted to get out and back to T3, if I went through the drop-off area I know I would be charged for "dropping-off" regardless of whether I actually did or not. So instead I entered the short stay car park and went straight to the exit, my thinking was there is a few minutes consideration period so if I pass straight through then I would be within that. However, when I get to the exit barrier it required payment, I don't know exactly how long it took me from entering to exiting but it would be no more than a couple of minutes, definitely well within 5 minutes. I just paid the fee so I could exit but not sure if I should have done.
So my question is, what are the rules around consideration periods, should this have applied or do they have something that exempts them from having to give this?