What's behind Starmer's trans U-turn?

Keir Starmer today seemed to change his party's stance on self-identification for transgender people. Before, Starmer said Labour would update the Gender Recognition Act so transgender people could self-identify as whatever gender they wanted. Today, he said that 'if you’re going to make reforms, you have to carry the public with you.' What's changed? 

Max Jeffery speaks to Katy Balls and Kate Andrews.