When Bank of America, America's largest bank (or it was earlier in the week) bought investment bank Merrill Lynch for $8bn last year it was hailed as a big sound bank buying a credit crunch-blasted Wall Street investment bank. Well Merrill Lynch, the thundering herd as it's known after its bull logo and the aggressive style of its traders, has proved to be even more rickety than anyone thought. Bank of America has just had to go cap in hand to the US government for a further bailout of $20bn and underwriting of $118bn of toxic assets, presumably inherited from those blasted bulls. The move will fuel fears that banks across the world will require a further round of bailouts as they find they don't have enough capital to support all the rubbish they have bought and plonked on their creaking balance sheets. Shares in UK banks have been plummeting all week due to this with some observers saying that Royal Bank of Scotland will go from 57 per cent owned by the Government to 100 per cent and even Barclays, which has chosen to raise more capital from investors abroad, may be forced to ask for further funds from the Treasury (ie taxpayers). What the banks need to do is write down all these dodgy assets to almost nothing so that someone, somewhere will be brave enough to take a punt and buy them. But that indeed means they will need more capital. So here we go again.