Clifford Chance is advising the Bank of England, which guaranteed an emergency facility for Northern Rock in the wake of the credit crunch.
It is understood that Clifford Chance has been advising the central bank for the last ten days.
Northern Rock has turned to magic circle rival Freshfields Bruckhaus Deringer, although the Bank of England is also a longstanding client of the firm.
Slaughter and May is advising the Treasury and the Financial Services Authority (FSA) with Goldman Sachs on their advice to the beleaguered mortgage lender.
Meanwhile, it is understood that US hedge fund Cerberus turned to favoured advisers Ashurst. It is mooting an approach for Northern Rock.
If Cerberus goes ahead in that approach its sole rival would be private equity house JC Flowers, which historically uses Sullivan & Cromwell and Cleary Gottlieb Steen & Hamilton for its legal advice. JC Flowers reportedly has undertaken due diligence on Northern Rock and has also instructed Credit Suisse.