In the most turbulent week in the financial markets for four years, there have been not only tears but also laughter as black jokes have helped some of the world's biggest banks and institutions come to terms with the prospect of huge losses.

As the FTSE 100 shed 4.1 per cent on Thursday - the biggest daily loss since March 2003 - traders let rip with expletives and gallows humour in equal proportions as they grappled with the volatility.