The following week Cook appeared in the German Open Championships in Bonn and took his maiden senior open title. In the final he defeated his fellow British competitor Davoud Etminani 12–11. He then went to compete and secured his place on the British team for the 2007 World Taekwondo Championships at a closed-door round robin competition held at Loughborough University. At the 2007 World Taekwondo Championship he defeated Gauti Mar Gundason of Iceland in the first round. In the second round he faced the toughest opponent of his young career, Hadi Saei of Iran who had won gold medals at both the 2005 World Taekwondo Championships and the 2004 Olympic Games. Cook could not get past the experienced Iranian and lost with a score of 11–6.