A London Ambulance Service spokesperson said:
“We carried out planned testing of our call answering system overnight but due to a technical issue we have been unable to switch back the system as normal, and are currently recording and allocating calls manually.
“Our staff are trained to operate the 999 system manually and we are continuing to prioritise our response to patients with a life threatening condition using the same assessment process as usual.
“Engineers are looking into this and will resolve the issue as soon as possible.”
More top news
London mayor Boris Johnson is backing Olympics supremo Seb Coe as his replacement.
Two police officers helping to guard diplomats have been sacked for sharing pornographic images on their mobile phones.
A 32-year old man from Hampton has been jailed for five years historic sexual assaults in the late 1990s.