The two MPs exchanged heated words over the issue of Islamophobia and claims of racism that have tainted the campaigns in recent weeks, with Goldsmith rejecting claims that he had be running an Islamophobic campaign.
"This is nothing to do with Islam.... this is very simply about your judgement," he told Khan.
His rival candidate responded: "I don't think you're racist or Islamophobic... he is a good man. He was fizzing with ideas but these have been drowned out by the campaign."
Watch the moment they clashed over these claims below.
And that was just the start of the debate.
Both men battled it out over their vision for the future of London, with housing, transport and jobs all top of the agenda.
But who emerged victorious? Check out the video below and decide for yourself.