A woman in her 70s died and 18 people were injured in two separate crashes.
The woman died after a car ploughed into a Costa coffee shop in Westerham, near Sevenoaks in Kent, shortly before 10.30am on Christmas Eve, leaving five other people injured - four seriously.
Pictures on social media showed an Audi embedded in the front of the cafe and a host of ambulances and fire engines at the scene in The Green.
Passer-by Tony Lincoln described the carnage left by the crash, saying ''it was almost as if a bomb had gone off''.
He was sitting at another coffee bar about 10ft away when out of the corner of his eye he saw ''a black flash which was obviously the car mounting the pavement followed by a huge bang''.
He crossed the road and forced open the door of the Costa shop which was jammed with debris. The room was clouded with dust and someone inside was almost hysterical.
Saying he had never seen ''anything as horrific as that'', Mr Lincoln told Sky News: ''It was carnage in there."
Elsewhere on Christmas Eve, seven people were taken to hospital after a bus crashed into a charity office following a collision with a car.
Witnesses said they heard a loud bang and then saw passengers with bloody noses as the single-decker bus ploughed into a Guide Dogs regional office in Peterborough.
Stagecoach said a motorist had come out of a side street and hit the bus, causing it to be ''pushed into the building'' at around midday.
The East of England Ambulance Service said that 13 people were injured but ''none appeared to be in a critical condition.''
Firefighters from Cambridgeshire Fire and Rescue used specialist cutting equipment to rescue the woman driver, who is in her 50s, and her female passenger from the car.