Top investment banks are struggling to cope with the record volume of deals and their overworked staff around the world are in danger of making costly mistakes, according to senior executives. Executives at Goldman Sachs, Morgan Stanley, Citigroup, JPMorgan Chase, UBS, Credit Suisse and Lehman Brothers all say their investment banking departments are under pressure. The banks have failed to hire aggressively, partly because they did not think the boom would last this long, and now privately admit they are suffering from serious staff shortages. Bankers say the problems are serious in New York and London but even more acute in smaller centres in continental Europe and Asia.