Sandler O'Neill Partners, the US boutique, has won its largest M&A mandate, jointly advising bank North Fork on its $14.6bn (€12.2bn) sale to Capital One Financial, the US credit card issuer, alongside Keefe, Bruyette & Woods.

James Dunne, senior managing principal, Brian Sterling, principal and co-head of investment banking, and John Ziegler were the lead Sandler O'Neill bankers on the deal.