Actor Brian Cox and historian David Starkey clash during a discussion over the relationship between Ed and David Miliband who both fought for the Labour leadership.
David, who lost to Ed, will move to the backbenches and not run for the shadow cabinet.
David Starkey said that David Miliband had "stabbed his brother in the back" and that the Labour party is "like Richard III murdering his nephews."
Mr Cox reacted by telling Mr Starkey that his comments were "provocative".
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