The financial clouds that have hung over Google all year parted yesterday as the search company revealed that it had yet to see much impact from the US slowdown and that changes to its search advertising system had not led to a feared slump in growth.

The news prompted the sort of celebratory rally that Wall Street had been accustomed to before this year's change of mood, sending Google's shares up 18 per cent in after-market trading to $529 and adding $25bn to the company's market value.