Sadiq Khan has won an historic third term in City Hall as he secured a resounding victory in the London mayoral election.The Labour incumbent outscored his main rival, Conservative Susan Hall, in nine of the 14 constituencies that declared their results on Saturday.Mr Khan secured 1,088,225 votes to 812,397 for Ms Hall - some 275,828 more.Ms Hall outpolled Mr Khan in Bexley and Bromley, Havering and Redbridge, Croydon and Sutton, Ealing and Hillingdon and her home turf of Brent and Harrow.