The New York Times reports that last week John J O'Brien pleaded guilty to four misdemeanour tax charges laid against him by federal prosecutors in Manhattan.

American authorities allege that O'Brien failed to file income tax returns for the period between 2001 to 2008. It is thought that O'Brien earned in excess of $10 million during this period. It has been alleged that O'Brien used this money for a range of personal expenses, including the maintenance of a rare books business and international travel.

O'Brien, who left Sullivan & Cromwell in 2009, will be sentenced on 16 November. He faces a penalty of up to four years in jail.

Just last month, American authorities charged Theodore Freedman, a former partner at Kirkland & Ellis, with tax evasion of over $2 million