Tom Steyer - US Democratic Party funder

As Donald Trump and family revel in the pomp and circumstance of a state visit to London, his staunchest political opponents continue to plot a pathway to impeachment. Stephen Sackur interviews Tom Steyer, a Californian hedge fund billionaire turned deep-pocketed backer of liberal causes, and he is funding much of that effort. His focus was climate change, now its impeachment. He’s a powerful force in the Democratic Party – but is he in danger of pushing the party in the wrong direction?