Richard J
Or am I missing something?
H4 has a 1500 ft height restriction at that point and so helicopters usually do fly above 1,000 ft as they pass this building. Typically I will be at 1450 ft. At 1300 ft and beyond we can pass directly over the top of the building without breaching the 500 ft rule, though typically we do not, heading towards the centre of the river. Therefore the separation from the building increases - it is 500 ft clear, not 500 ft above.
When landing into Battersea we need to come down from this height - as PB was doing on this occasion. Once we are in that stage of flight the 500 ft rule does not apply and so passing within 500 ft of an person, vessel vehicle or structure is not prohibited.