Thanks for the reference Talkdown man, apparently LHR controllers do have available procedures (albeit during DAY and VMC) that are not being utilized
3.8.3 Land after Procedure
3.8.3.1 Normally, only one aircraft is permitted to land or take-off on the runway-in-use at any one time. However, when the traffic
sequence is two successive landing aircraft, the second one may be allowed to land before the first one has cleared the runway-in-use,
providing:
a. The runway is long enough;
b. it is during daylight hours;
c. the second aircraft will be able to see the first aircraft clearly and continuously until it is clear of the runway;
d. the second aircraft has been warned.
ATC will provide this warning by issuing the second aircraft with the instruction 'land after ....... (first aircraft type)' in place of the
usual instruction 'Cleared to land'. Responsibility for ensuring adequate separation between the two aircraft rests with the pilot of
the second aircraft.
3.8.4 Special Landing Procedures at London Heathrow, London Gatwick and London Stansted Airports
d. When issuing a landing clearance following the application of these procedures ATC will issue the second aircraft with the
following instructions:
London Heathrow and London Gatwick
....... (call sign) ....... after the landing/departing ....... (Aircraft Type) cleared to land Runway ....... (Designator).London Stansted
....... (call sign) ....... after the departing ....... (Aircraft Type) cleared to land Runway ........ (Designator).
Now why are they not being used? In over 20 years of flying into LHR I have never heard it used.