The Hollywood star - famous for roles in The Fresh Prince of Bel-Air and Men in Black - met students at St Martin-in-the-Fields High School for Girls in Tulse Hill, doing a question and answer session and signing autographs.
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Police are investigating whether a Land Rover Defender found burnt out in West Horsley was involved in Tuesday night's ram raid.
The work, called Gift Horse, replaces the giant blue cockerel that previously sat on the plinth.
50 of the country's worst pollution blackspots are in the capital. Many in places you may visit every day.