Tottenham Hotspur slumped to a 1-0 defeat in the North London derby as they were again undone by a set-piece goal. Arsenal recorded a third successive victory at Tottenham Hotspur Stadium as Gabriel Magalhaes’ header just past the hour mark proved decisive in the derby. The Arsenal defender lost Cristian Romero to get on the end of Bukayo Saka’s corner and thump a headed attempt past Guglielmo Vicario. Ange Postecoglou has been urged to add a set-piece coach to help with their weaknesses on set-pieces, but contrary to belief, the North London club already have a coach who is working to improve…