Although Manston has long since closed, why is there not another less busy airport to land at in such a situation. Apart from all of those aircraft diverted from Gatwick, what about those landing at Heathrow using Gatwick as their alternate. Did they all carry enough fuel to go elsewhere?
It would appear that landing back at Gatwick could have compounded the problem?
The Captain decides where to land. ATC may have read their "please bog off elsewhere script" (LHR does, not sure about LGW?), but Capt has right to override.
I doubt there are many other airfields with the same runway length / crash cat. Engineering cover might, in this case, also be a factor to rapidly assess situation v status of the gear.
Anyway, where do you think the Capt's car was parked
NoD