If UK Chancellor Alistair Darling wanted advice on how to maintain the Government’s top-notch rating on its debt he could find far worse places to turn to than Wellcome Trust, one of the world’s largest endowments.

Last week, rating agency Standard & Poor's renewed the UK charity's AAA grade, plus the 30-year, £550m bond it issued in 2006. On the same day, S&P downgraded Ireland's AAA credit grade to AA+, warning the country needed better control of its public financing. The UK Government could be forgiven for looking nervously at the impact of its deficit on its sovereign rating.