Why are the UK's borders still open?

Following the announcement of a third lockdown, a testing regime for arrivals could be put in place. It comes as Michael Gove said there would be announcements in the coming days about 'how we will make sure that our ports and airports are safe', and Nicola Sturgeon said 'urgent' discussions were underway. Isabel Hardman talks to Katy Balls and James Forsyth.