An air raid siren sounded over Greenwich today as more than 60 firefighters battled a blaze at a chemical processing plant.
The alarm was sounded as a precaution after the fire at the factory threatened to affect a unit containing hazardous chemicals.
@4tea2 sent us this video of the siren:
The incident, which saw smoke fill the air around the unit on Peterboat Close, has now been brought under control.
The warehouse on fire contained "swimming pool chemicals" but the siren was sounded to alert the public to "more dangerous chemicals" in a nearby building.
This building, one of only a few in London required to have a siren for safety reasons, was not affected by the fire but London Tonight has been told the alarm was sounded as a precaution.