17: Know your enemy: Opposition research and preparing for PMQs; With Tom Hamilton

In politics as in battle, it's vital to know your enemy. Getting inside their head to anticipate their likely attacks and prepare your own defences, as well as seeing your respective weaknesses. Tom Hamilton was Head of Research for the Labour Party for 10 years, and helped prepare Harriet Harman, Ed Miliband and Jeremy Corbyn for Prime Minister's Questions. He talks to us about how oppositions prepare for battle in debate.