Warren East, the newly-appointed boss of engine maker Rolls-Royce, is to step down from his position on BT's board after just 14 months, the telecoms group announced.East, the former ARM chief executive officer (CEO) who was unveiled as John Rishton's replacement at Rolls-Royce on Wednesday, joined BT in February 2014 and currently sits on the pensions, audit and risk committee and technology committee.BT said he would step down as a non-executive director on 31 May before joining Rolls-Royce in July.East said in a statement that his time at BT was "all too brief". "I wish the company great success which it surely deserves," he said.BT chairman Sir Michael Rake said East "made an immense contribution during his time at BT and I congratulate him on this important appointment".BT's share price was up 0.9% at 460.95p by 15:48 following the announcement, helped higher by a target-price upgrade at broker Nomura.