Freshfields Bruckhaus Deringer's US practice has bagged one of its largest-ever mandates, advising a consortium on its bid to operate one of the busiest motorways in the US – a project valued at around $15bn (£7.3bn).

Freshfields is advising a consortium headed by Australian investment house Babcock & Brown, which is considered to be a front-runner in the Pennsylvania Turnpike project – thought to be the largest-ever project of its kind in the US.

While it is not yet clear which bidder will succeed, the deal is a coup for the magic circle law firm, which beat a number of Wall Street firms to the role.

White & Case is advising a rival consortium, backed by Macquarie and Spanish highway company Cintra. The US law firm has advised both clients on a number of multibillion-dollar projects in the past.

Meanwhile, the State of Pennsylvania has called in infrastructure specialist Ballard Spahr Andrews & Ingersoll.

Last month the bidding companies were formally asked to submit credentials for running the highway, although there has been political opposition surrounding the privatisation of the road.

Freshfields has had a relatively low profile in the US in recent years. Notable mandates the US practice has bagged include advising on the first-ever rail public-private partnership in California, the Bay Area Rapid Transport District, and advising Siemens on the US aspects on its E4.2bn (£2.9bn) purchase of Bayer's diagnostics division.

However, the magic circle law firm has been attempting to build its US capability in recent months. In August the firm relocated litigation partner Brian King to New York from Amsterdam along with three associates, while corporate partner Julian Pritchard moved across from Tokyo.

The UK firm has 100 US-qualified lawyers in offices around the world, primarily based in New York and Washington DC.

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