A second arrest has been made over the death of PC Andrew Duncan after he died from his injuries following a hit and run collision on Friday.
The Met have confirmed a woman has been arrested on suspicion of perverting the course of justice. She remains in custody at a South London police station.
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The 24-year-old was unarmed and the incident is not being treated as terror-related.
Some platforms have been taken out of service with disruption expected to continue until the end of the day.
The Met Office has extended its weather warnings for snow and ice to cover vast swathes of the country, including London and the South East.