How do the police carry out a 'hard stop'?

Mark Duggan, whose death sparked riots in England in 2011, was lawfully killed, an inquest jury has said by a majority of 8 to 2.

The 29-year-old was killed in August 2011 in Tottenham, north London, after police stopped a taxi in which he was travelling.

Using footage from a training exercise conducted by the National Crime Agency, the BBC's Danny Shaw explains how police conduct a hard stop - which was the kind of tactic used when Mark Duggan was pulled over.