Speaking to ITV News ahead of tonight's switch on in Oxford Street, Jessie J said Christmas helped put London in a good mood - which was what the capital sometimes needed.
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Police in Southwark are appealing to the public for help in finding a teenage girl missing from Bermondsey.
Over 40,000 people picked up their packs to take part in the annual marathon in the capital.
The boyfriend of reality TV star Ferne McCann has been arrested on suspicion of attempted murder following an alleged nightclub acid attack.