Mail Online—Twitter users are reporting hearing a large 'explosion' across London and as far north as Hertfordshire.
Loud ‘explosion’ heard across London sparks mass panic. Frightened Londoners already frazzled by Friday’s London Bridge attack thought they were under attack for a second time when a loud “explosion” was heard across the city on Sunday morning. It turned out to be a sonic boom from Royal Air Force fighter jets. But the thousands of residents who were awakened by the sound