The singer, who performed solo on The X Factor at the weekend, made an appearance at London's Westfield shopping centre yesterday to launch Reebok's new ZigTech trainers as part of an endorsement deal with the brand.

The new ZigTech footwear features a unique zig zag sole, which apparently absorbs the impact of your heel as you run sending a wave of energy along the shoe. The new range is being referred to by the brand as an 'energy drink for ...