They showed the flight path on the Look East news this morning. I'm kind of surprised it got that close to London when it wasn't communicating.
I imaging there was a serious brown toruser moment in the cockpit when a couple of supersonic Typhoons turned up.

I used to live near a military airport in Bavaria, they had Tornados and Typhoons. There were regular sonic booms (several times a month) as they did training flights.

The good part of living somewhere where there are regular sonic booms is that it dislodged dust in the hard to reach places.

Being Germany, they weren't allowed to go supersonic during the Mittagsruhe (Mid-day peace), which is between 1pm and 3pm (and after 8 in the evening).