It was announced by Heathrow last year that the dropoff zone outside the terminals were going to be subject to a £5 charge, and this charge commenced last Oct 21.
However it appears that Heathrow have not quite got themselves sorted to start to fleece the good folk using LHR T4 until the 1st July.
from the Heathrow website:
The Terminal Drop-Off Charge at Terminal 4 commences on 1 July 2022 at 00:00. If you are dropping off at Terminal 4 prior to this date you do not need to pay the charge.
So if you're traveling with Qatar and get driven to/from the airport using the drop off zone during June 2022 make sure you don't pay the additional £5, some taxi drivers might accidentally-on-purpose include it in your fare.