British team members (from left) Nethaneel Mitchell-Blake, Richard Kilty, Chijindu Ujah and Zharnel Hughes celebrate coming second in Tokyo. PHOTO: AFP

PARIS (AFP) - The British men's 4x100m relay team have handed back their silver medals from the Tokyo Olympics after Chijindu Ujah tested positive for a banned substance, the British Olympic Association (BOA) said on Thursday (April 14).