Cockerell: May's message 'we're watching you'

It's not often - if ever - that you see the prime minister in the House of Lords. And yet Theresa May chose to go and watch the debate on Brexit there yesterday. Why?

What did she hope to achieve that she couldn't have learnt from listening on the radio or watching on television? The BBC documentary maker Michael Cockerell told the Today programme she wanted to send the message "I'm serious about this bill, don't you muck about with it".