Roger Stone - US political strategist

Stephen Sackur speaks to the American political strategist Roger Stone. They say you can judge a man by the company he keeps. If that's true, Roger Stone, a long-time friend and sometime advisor to president Trump, should be able to provide telling insights into the character of the president. He is a hugely controversial and divisive figure in American conservatism, is he also a symbol of all that's currently wrong in US politics?