A dog was killed after being thrown from a moving vehicle on the M25 with a second dog surviving the impact.
Cars were forced to swerve and break suddenly after the two dogs were thrown along with a blanket.
One dog, a lurcher type, was killed instantly after being hit by other cars. The second dog, a small black and white Jack Russell terrier, dodged the slowing traffic and made it to the side of the road.
The Jack Russell was checked over by a vet and has no serious injuries. He was not microchipped.
Anybody with any information that may help the RSPCA can call in complete confidence, on 0300 123 8018.