Just heard a helicopter and sirens and assumed it was police. But I’ve just seen the helicopter landing so presumably it’s a medical emergency. From here it looks like it landed near one of the building-site cranes on Mayow Road - the one opposite Wynell Road? Not saying that’s the scene of an accident, just near where the helicopter looks like it was landing.
And now there’s a police helicopter circling.
I’ve seen on Facebook that someone has said their husband has just seen a “horrific accident” on Mayow Road outside the park. 
Just had a quick look and can confirm. Mayow Rd is taped off south of Wynell Road - didn’t get close but there was a 75 bus in the taped off area, plus an ambulance and police presence.
Air ambulance has just left. My thoughts are with whoever was injured and I hope they make a good recovery.
I thought the first helicopter sounded lower than the normal police one.
According to some eyewitness posts on Next Door there was a car chase involving the police on Mayow Road. Someone who claims it happened right outside his property but wasn’t being allowed to go into his property has said “temporary traffic lights for roadworks plus a bus stop made a police chase very tricky causing a massive accident”. One of the police at the scene has said there are injuries and apparently Dacres Rd, Queens Rd and Mayow Rd are all blocked. Lots of unmarked police cars are in the area so sounds quite serious.
Apparently a car was on its roof. Not good 
Details of diversion route for 75 bus from TfL website:
MAYOW ROAD (SE23/Lower Sydenham): Route 75 diverted:
Due to a road traffic incident and a police-led incident, Mayow Road is closed to all traffic in both directions and all buses on route 75 are on diversion via Sydenham Road, Bell Green and Perry Rise until further notice, missing the section of route and all stops between Earlsthorpe Road and Siddons Road (both directions)
Sad to hear that it’s two innocent people who ended up injured as a result of this incident yesterday. I hope they both make full recoveries from their injuries.