A 10-year-old girl was seriously injured after reportedly walking out from between two buses and getting hit by a white van in Thamesmead.
The accident happened just before 12.30pm in front of Coralline Walk in Yarnton Way just in front of Lakeside Medical Practice.
'Hero' Glen Mewes, 44, of Coralline Walk, heard a "loud bang" and rushed out of his house to see what had happened and he said he saw the girl lying in the road with her legs poking out from under the van.
He told News Shopper: "Instinct just kicked in and I ran down the stairs to see if she was ok. She looked unconscious which was a bit scary but I just kept calm and went into the medical centre to alert the staff.
"Other passer bys called 999 and medical staff were quickly giving her first aid and tending to her.
"Within a couple of minutes there was a big crowd of people at the scene. We heard the girl had just walked out and not looked and then the van hit her.
"The van driver collapsed against the van in shock after it happened. The girl's brother turned up and he was just in pieces.
"She was talking and told us where she lived and was conscious before she went to hospital."
Neighbours said a crossing was "desperately needed" outside the medical centre because of the amount of school children and people using the road.
Belinda Bull, 45, of Coralline Walk, Thamesmead, added: "There used to be a bridge to get over the road which has been taken away to make it more open spaced.
"There are no crossings and it's very dangerous now, especially for children and the elderly."
"They should at least put in zebra crossings or traffic lights.
"I've been here for 12 years. There's been so many accidents, especially in the area by the BP garage.
"There was blood on the road, she must have hit the windscreen quite hard because there's a big crack in it."
"My friend Kim's husband, Glen, was actually the one who went to go and get the nurses from the pharmacy after it happened. He's the hero."
Head of bus operations at TfL Ken Davidson said: “At around 12.30pm today a 10-year-old girl was involved in a collision with a van on Yarnton Way at the junction of Harrow Manorway.
"The collision resulted in the pedestrian being knocked under a stationery route 180 bus, operated by London General."
A TfL spokesman said: "Yarnton Way is currently closed westbound from Harrow Manorway. Bus routes 180, 401 and B11 are on diversion."
A police spokesman said: "We were called at around 12.50pm to reports of a collision between a bus and a pedestrian in Yarnton Way.
"The pedestrian is believed to be a 10-year-old girl who has been taken to hospital with serious injuries but it is not believed to be life threatening."
A London Ambulance spokesman added: "We were called at 12.33pm and sent a single responder, ambulance crew and air ambulance and treated one patient at the scene.
"She was treated for head leg and arm injuries and was taken to Kings College Hospital by road ambulance and was accompanied by the doctor from the air ambulance."