Nevertheless. If Gatwick single runway ops can deliver over 50 per hour on one runway that kinda points at 100/hr at LHR. Or am I missing something?
Yes, you're ignoring the fact that the Gatwick runway operates, of necessity, in mixed mode whereas under normal circumstances Heathrow's runways operate in segregated mode, which is less efficient in terms of utilisation.
I've read estimates that LHR could accommodate around up to 15% more movements without extending the operating day if full mixed mode was used on both runways. That would be a more realistic comparison with LGW's capacity.