Almost to the day one year ago, Tesco gained a new chief executive. Sir Terry Leahy, who had transformed the retailer from a £4bn business to one with a value of £32bn, handed over the reins to his successor Philip Clark. As we all now know, Tesco has tripped up badly since that handover of power - ground has been lost to rivals, there's been a shock profit warning and slump in the share price - and the new CEO has admitted to making strategy mistakes. Even shareholders who don't own a stake in the giant grocer must be watching intently from the sidelines because at the heart of the story lies an issue that affects all big and successful companies: that of succession planning. No matter how brilliant the CEO, he, or she, isn't going to stay forever. And when the time comes to appoint a new boss, shareholders have to decide if they should throw their lot in with the new boss or get out fast before things go wrong. It's an issue that's been raised by the world's most famous investor, Warren Buffett, in his annual letter to Berkshire Hathaway investors, almost certainly several years in advance of a change at the top. But with a compound annual gain of almost 20 per cent, an overall average gain of 513,005 per cent since the mid 1960s and a current share price of $120,000, there's a lot at stake. Mr Buffett says a successor has been identified, along with two superb back-ups, and that they "will enjoy a running start". Even so, he knows that his are big shoes to fill. You can read the full letter to shareholders at www.berkshirehathaway.com. Meanwhile, in Simon Thompson's letter to readers this week, he analyses the current bull rally and whether it has further to run, along with the implications for small cap shares. We've also got the latest news and our updated views on Discovery Metals - which has doubled since we tipped it at 52p, HSBC, Asian Citrus and Netcall, along with our start of the week round up of press tips.