Eddy Joaquim via Getty Images
An off-course pod of porpoises have been spotted in the Lambeth area, following initial sightings near Tower Bridge.
Scotland Yard's Marine Policing Unit reported the rare sightings on Twitter this morning, saying the mammals "seem happy enough."
The sightings follow another lost dolphin getting stuck in Chester city centre in August.
But the confused creature's adventure came to a happy end - after he has been spirited back to the sea after gaining a great array of nicknames from locals including the Great Dee Rivermonster, the Dee Dolphin, and Dave the Dolphin.
The lost dolphin had taken up residence in the River Dee