The London Ambulance Service says it expects its 999-call computer system to be back up and running "in the next hour or two."
A spokesman said that the technical issue had been identified and that they were now bringing the system live again.
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"All it takes is for somebody to see me - and I could just die, just like that. I could want to go to the shop and not come home."
Before the killing, Peters searched the internet for "serial killers", "treatment of child killers in prison" and "premeditated murder".
Arriva Rail North, Greater Anglia and South Western Railway are all affected.