What is going to make this more difficult is:
The Terminal Drop-Off Charge is payable online, via mobile phone, automated telephone service or by autopay functionality
The service is operated via Automatic Number Plate Recognition (ANPR) - there are no barriers in the Drop Off area
There are no gates. For those who do not use the place often, or for the first time, they might be late in registering or paying. You may be certain that the outsourcing of this is to a company that expect to make more than just their percentage of each £5.00.
I do understand that every company is trying to claw back money lost in 2020. The problem is that, all the little bits added to charges - across the span of activity - right down to the price of a take away drink in the terminal or the high street, will fuel inflation.