Perella Weinberg Partners has landed one of its biggest advisory mandates after Maurice Greenberg, former chief executive of American International Group, hired the independent investment and advisory firm to evaluate his stake in the company after ending a campaign for change at the US insurance giant.

Greenberg was chief executive of AIG, one of the world’s largest companies with a $137.6bn (€93.9bn) market capitalisation, until 2005, when he resigned as regulators were investigating the company’s accounts. AIG reached a $1.6bn settlement with regulators to resolve allegations of accounting fraud.