Conditional Line Up Clearances at LHR
I've just re-read the AAIB report on the BA/BM incident of April 2000, it mentions that at the time, Heathrow ATC were considering implementing a restriction on the number of conditional line up clearances. Having been given a couple of excessive clearances (as I see it) in the past few months, (for example: "line up 09R behind the BM 737 on the northside", where having counted, the BM 737 is ninth in the queue), I would be interested to know what the restriction actually is, and does it differ when single and dual landing runways are in use?
Not necessarily a criticism, just a query.