London's Olympic Ambassadors are back on the streets in a pilot project at St Pancras Station.
The volunteer force will offer advice to visitors on how to get to attractions, restaurants and shopping areas.
But, as Rags Martel reports, they started with something a bit more dramatic.
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The victim was fatally stabbed.
Doctors are wearing white surgical masks to represent the number of people who die prematurely from air pollution.
Daniel Fakoya, 18, of Priory Court, E17 was sentenced to 15 years in jail and a further three years on licence.