I once worked as a butler for a family who lived in the New Forest, Southampton.
One day, the Concorde flew nearby and I heard a gentle, but firm, sonic boom.
Guess what, That was Air France ignoring the rules. Odd that!!!
I was working in Alderney with Aurigny at the airport, and on hearing the sonic boom, and the guys there said that it was common as AF, when travelling down the channel, ignored the rules and went supersonic earlier than they should.
A good friend of mine reported that the boom was also heard in Bracknell..
He was told that the sound in effect bounced of cloud formation thus extending the noise area.