Allen & Overy (A&O) and Mayer Brown have taken lead roles on Baja Mining's $823m (£518m) financing facility for the construction and development of its flagship Mexican mining project.

Mayer Brown advised the lending group on the project financing, which is one of the largest of this nature to come to market. The completion of the deal means that full-scale construction activities on the Boleo mining project can commence imminently.

The finance facilities were provided by a group of commercial banks, which included Barclays Capital, Standard Bank, Standard Chartered Bank and UniCredit. Other lenders in the consortium included US Export-Import Bank, Export Development Canada, as well as Korea Development Bank.

Mayer Brown fielded a team led by global head of mining Ian Coles, who worked alongside mining partner Rachel Speight, construction partner Jonathan Hosie and derivatives partner Chris Arnold. Chicago-based projects partner Barry Machlin also advised on the deal.

Coles commented: "By anybody's standards the Baja mine is a world-class mining project.

"With the involvement of lenders from a variety of different backgrounds and with the complexity of the overall financing structure, the dynamics of the deal and the attendant negotiations were unique in many respects, and certainly presented new challenges to all involved."

A&O advised Baja Mining's project company Minera & Metalurgica del Boleo, fielding a team led by New York-based mining partner Robert Kartheiser. Endeavour Financial acted as financial advisers.