Graham Root, a credit derivatives and asset swap trader at broker BGC International in London, is leaving the firm and market officials have connected him with a sell-side credit role at SG Corporate & Investment Banking.Sophie Hoggarth, spokeswoman for SG in London, declined comment. Timo Kindred, spokesman for BGC in London, confirmed Root leaves this week and reports to Chris Lee, desk head of credit derivatives. Root and Lee could not be reached for comment.