Now that's interesting: I've just noticed that there have been 4 declared emergencies within 1 hour somewhere around London.
- Ryanair EI-DPZ, Birmingham to Bydgoszcz
- British Airways G-EUXE, Newcastle to London
- British Airways G-EUXG, London to Amsterdam
- Easyjet G-EZDX, Glasgow to London
Then there was an unrelated TAP CS-TQD from Lisbon to Paris, also squawking 7700 over France.
Was there anything special going on in London, like weather (but it doesn't seem to be bad according to the METAR) or some forced diversions for some other reason? Or just coincidence?