What can we learn from the Uxbridge by-election result?

The dust has settled after yesterday's by-election results. Having narrowly avoided a triple by-election defeat there seems to be little sign of Conservative party in-fighting, despite their poor showing. There is however a war of words brewing between the London Labour Party and Kier Starmer who blames Sadiq Khan's Ulez plan for the failure to snatch Uxbridge and South Ruislip. What lessons will each party take from the by-elections into next year's general election? 
 
James Heale speaks to Katy Balls and pollster James Johnson, co-founder of JL Partners.