Turkey's president Erdogan says the murder of Saudi journalist Jamal Khashoggi was a savage crime meticulously planned in Riyadh. He wants all those responsible to stand trial in Turkey. As the pressure on the house of Saud mounts, will the kingdom's partners in the west take punitive action? Stephen Sackur speaks to Alan Duncan, minister of state in the UK Foreign Office. Has the time come for Britain to stop lucrative arms exports to Saudi Arabia?