Londoners were treated to a rare cloud formation which gathered over the capital.
Pictures taken in south London showed clouds which resembled a ''black hole'' according to one social media user.
The unusual sight saw a flurry of images posted on Twitter accompanied by various descriptions which ranged from ''creepy cloud'' to ''what the hell is this?'
Twitter user Iain Mellis captured a wave-like formation in the centre of the capital.
The clouds were identified by experts as Asperitas, a rare formation which was only recently given a name.
According to the Met Office: “Asperitas is a distinctive but relatively rare cloud formation that takes the appearance of rippling waves.
“These wave-like structures form on the underside of the cloud to make it look like a rough sea surface when viewed from below.”
Exactly how the clouds are formed is not known, but they require unstable atmospheric conditions and are sometimes associated with the aftermath of thunderstorms.
Asperitas was officially recognised by the World Meteorological Organisation in 2015.
This is the second unusual weather-related sight this week.
On Monday it was reported sunsets and sunrises over the UK have been unusually colourful of late and it is mainly down to something happening thousands of miles away across the Atlantic ocean.
Social media users have been sharing stunning photographs of the early and late daily phenomena, with some admirers even questioning whether the pictures are real.
They are - the Met Office has confirmed - a reality and it is all to do with dust particles from wildfires in Canada have been swept across the Atlantic ocean by the jet stream.