Met Police officers scrambled to Barking Road in Newham at 5.11am on Sunday after reports of a collision between a car and a pedestrian.
A 35-year-old man was found injured yesterday at the junction with Arragon Road and died shortly after.
Later that day, at 3.30pm, a 33-year-old man was arrested at Heathrow Airport on suspicion of murder.
Cops also arrested a 30-year-old woman on suspicion of assisting an offender.
The pair both remain in custody, said the Met Police.
Detective Chief Inspector Joanna Yorke, who is leading the investigation, said: “My thoughts are with the victim’s family at what will be an incredibly difficult time for them.
“Our family liaison officers will support them as our inquiries continue.
“I am aware that a large number of people had been at an event in Barking Road overnight and many would have witnessed the incident.
“I am appealing for those people to come forward immediately. Your information could be vital to the investigation.
“Forensic collision investigators have worked at the scene throughout the day and, although we do not believe there to be any risk to the wider community, officers will remain in the area over the coming days to provide reassurance.”
She said although police do not believe there to be any risk to the wider community, officers would remain in the area over the coming days to provide reassurance.
Ms Yorke added: “My thoughts are with the victim’s family at what will be an incredibly difficult time for them. Our family liaison officers will support them as our inquiries continue.”
Anyone with information is asked to call police on 101 quoting CAD 1281/24Mar.
To remain anonymous contact the independent charity Crimestoppers on 0800 555 111.