A loud bang heard across Hertfordshire early this morning caused homes to shake, set car alarms off and led to many thinking a bomb had gone off in the county.

The boom, heard just before 4.20am, led to many calling the emergency services. At about 4.30am, Herts fire service tweeted: "We are currently receiving a large number of calls from across the whole of Hertfordshire regarding a large explosion sound. We are investigating."

Stevenage Old Town resident Julie Lucas said: "I thought we had been bombed - our whole house shook, waking everyone up and then my very laid back husband said it was the wind!"

The boom was also heard in London, and it was the Met Police who confirmed that it was due to RAF jets flying faster than the speed of sound.

The force tweeted: "The loud bang heard throughout north London and surrounding areas was the result of a sonic boom from RAF planes. There is no cause for concern."

The BBC reported: "The noise was generated by two Royal Air Force Typhoons, which launched from Coningsby in Lincolnshire and intercepted an unresponsive aircraft.

"The sonic boom was heard across London, Hertfordshire and Bedfordshire.

"RAF jets are only given permission to go supersonic in emergencies, usually when they are required to intercept another aircraft."