Partners at law firms Allen & Overy and Shearman & Sterling have voted “overwhelmingly” to combine their companies to create what they call the first fully integrated global elite legal operation.

The merger of the London and New York-headquartered companies will create a new superpower in energy and shipping markets.

Allen Overy Shearman Sterling (A&O Shearman) will have 3,950 lawyers and 800 partners across 48 offices, with combined revenues of $3.5bn.