A 34-year-old man was in a critical condition in hospital on Monday evening after being stabbed in south-east London.
Police and paramedics were called to Eltham, in Greenwich, at around 5pm on Monday along with London’s Air Ambulance.
The victim was found in Middle Park Avenue suffering stab wounds.
He was taken to hospital and remains in a critical condition.
A 20-second video posted online on Monday appeared to show the victim being stretchered across a park and into the air ambulance.
The Met said cordons were now in place but no arrests had been made.
At least 51 people have been fatally stabbed in London since the beginning of the year, according to media reports.
There has been 1,296 stabbings in London up to the end of April, according to the Met.
Crime statistics last week revealed the total number of offences involving a knife or bladed instrument in the year to March 2018 jumped 16% to 40,147 - a seven-year-high.
In the 12 months to March, forces in England and Wales logged a total of 5.5 million offences, a rise of 11% compared with the previous year.
Excluding cases linked to terror attacks and the Hillsborough disaster, the number of recorded homicides increased by 12% year-on-year, from 627 to 701.