Olympic Ambassadors will be back on the streets of London today. Volunteers will be in "pods" at St Pancras International Station to welcome tourists arriving on the Eurostar.
It's the first of a series of pilots to test the project. There are 55 volunteers taking part.
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Four men have been arrested after a 21-year-old man was murdered in Lewisham
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Scotland Yard said the male youths will appear in custody at Westminster Magistrates' Court on Saturday.