What should Keir Starmer do with the Batley and Spen win?

In an extremely close race Labour candidate and sister to the late Jo Cox Kim Leadbeater has won her by-election with a majority of just 323. What will the opposition do with this narrow but note worthy win? And is it time to for the tories to admit they aren't as invincible as they first thought? To discuss Katy Balls is joined by James Forsyth and Isobel Hardman.