20 a. m. didn' t know that - and made a frenzy of emergency calls to authorities to report an obvious explosion that had made their houses shake.
The metropolitan police quickly tried to calm the public by saying "there was no need to worry" and explaining the harmless origins of the sound. "Heard a loud explosion and police sirens around 4:10 am".
Typhoon jets were scrambled after an aircraft lost communications, it said.
Twitter consumer Natasha wrote: 'Simply been woken up by a large explosion in North West London.
Around 15 minutes later, police added on Twitter: "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 company tweeted on Sunday morning.
Nevertheless, the force of the explosion caused fear in the hearts of the British when it was heard across London, Hertfordshire and up to 100 km from Cambridge, shaking houses and waking people up in panic.
The two jets were launched from the RAF base in Coningsby, Lincolnshire just after 4.00am GMT and intercepted an unresponsive aircraft.
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Hertfordshire Fire and Rescue said it had received a large number of calls from across the county regarding a "large explosion sound".
The planes scrambled after an aircraft lost communications while in United Kingdom airspace.
Sonic booms are caused when an aircraft travels faster than the speed of sound.
Earlier this year, two RAF Hurricane fighter jets precipitated sonic booms over the east of England.
After communications with the aircraft were restored, the flight continued as planned toward the USA and the fighter jets returned to their base.
The noise is often heard as a huge thunderclap.