Actor Will Smith offered some words of advice, as he addressed teenagers at a school in Tulse Hill.
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Members of the GMB union are protesting at changes to pay arrangements, including moving from weekly to monthly pay.
Transport for London gave away more than 22,000 travel passes last year under the 'Staff Nominee' scheme.
The horrific attack happened at around 10:45pm on a grass area near Barge Walk, in Kingston, south west London.