RAB Capital, the London-listed investment manager which has taken a 6.6 per cent stake in troubled UK bank Northern Rock, increased its assets under management by 6 per cent to $7.1 billion in the three months to the end of September. Half the increase in assets between June and September came from the acquisition of Pi Investment Management, a Hong Kong hedge fund manager. The deal was announced in June and completed this month. RAB Capital, which was founded in 1999 and floated in 2004, said its assets under management had risen 75 per cent compared to the end of September 2006. It said it has 15 funds with more than $100 million each. Its largest fund is the special situations fund, run by RAB chief executive Philip Richards, which has more than $2.3 billion of assets under management. Its energy fund, which has a common exposure to industry sectors as the special situations fund, has more than $1 billion.