Police Commissioner Bernard Hogan-Howe will visit a school in Edmonton today that was blighted by knife crime.
Negus McClean was stabbed to death by a gang a year ago, following a fight over a BlackBerry mobile phone.
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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.