Lloyds Banking Group has announced its contingency plans in case chief executive Antonio Horta-Osorio extends his stress-related sick leave. Tim Tookey, who stepped in as interim head earlier this month, is due to leave Lloyds in February. Now, the bank has said that David Roberts will become interim chief executive if Mr Horta-Osorio does not return before the end of the year. Lloyds said \"Antonio is continuing to make good progress in his recovery\". The bank had announced on 2 November that its chief executive was taking extended leave due to stress-related illness. David Roberts has been a non-executive director of Lloyds since March 2010 and is chairman of its Risk Committee. \"David Roberts has impressed his colleagues on the board and the group\'s senior management with his understanding and broad experience of the banking and financial services sector,\" said Lloyds chairman Sir Win Bischoff. Lloyds also announced that Nathan Bostock, who it had announced July would be leaving Royal Bank of Scotland to become its new chief executive for wholesale banking, had now decided to stay at RBS. Lloyds shares were down 6.7% in lunchtime trading, the worst performing stock on the FTSE 100 index.