You can read an overview here:
https://www.heathrow.com/file_source...k_Nov_2016.pdf
Heathrow management has some delegated powers to allow exceptional cases, but they must follow the rules.
Originally Posted by
KeaneJohn
To my knowledge there are no restrictions and any airline can land at any time.
Aircraft noisier than QC/4 are not permitted to operate in the night period 23:30-06:00 (except, I assume, in emergency).
Noisier than QC/2 are not permitted to be scheduled in the night period.
Fortunately for the passengers in this case, a 767-300 arrival is QC/0.5