Saudi Arabia's has promised a ‘serious' response after a weekend of Houthi attacks, but there are fears the escalation of the war could draw in other players. Professor Bernard Haykel, who has specialised in the political and social history of the Arabian Peninsula, tells Channel 4 News that Saudi Arabia might need mercenaries ‘to get Houthis to back down’. #Saudi #Houthi #Riyadh #C4News