Singer Ellie Goulding came to the aid of a driver being pushed sideways by a Royal Mail lorry in west London.
Footage shows a Volkswagen GTi being pushed down Western Avenue, A40, by the delivery vehicle near to the Greenford roundabout.
Goulding posted on Instagram to criticise other drivers who got out to film the crash and “shout abuse” at the Royal Mail driver.
The Royal Mail says it is investigating the crash.
The truck driver appears astonished to see the car in front of his vehicle, claiming he did not see it, or know it was there.
He can be heard yelling: “I didn’t see him, I honestly didn’t see him.”
Goulding told her 14.4 million Instagram followers: “On a side note, I can’t believe the first instinct of the other drivers who got out was to instantly start filming on their phones and shout abuse at the poor shocked driver, not even checking the other driver was okay.
“What on earth.”
The Met Police said there were no reported injuries and no arrests have been made.
A Royal Mail spokesman added: “We are very concerned about this incident. We sincerely hope that no one was hurt. We are investigating as a matter of urgency.”