Simmons & Simmons and Newcastle firm Dickinson Dees have completed work on a ground-breaking £98m public private partnership deal to put into place a Sunderland metro extension.
The deal was unique because it will allow the running of lightweight metro trains on the national rail network - the first example of track sharing in the UK.
Simmons has had a team of eight working on the deal for more than a year, thrashing out complicated legal issues concerning connecting regulated and unregulated networks.
Dickinson Dees acted for the Tyne and Wear Passenger Transport Executive (Nexus) on the deal.
Simmons commercial partner Juliet Reingold, who led the team, says: "Having to fall within the regime of the rail regulator for the first time meant that we had to work with Nexus explaining how the national rail network operated.
"It was a very important deal for Railtrack, which has committed £40m of its own money to the project.
"This is a classic example of the integrated transport system."
The three-lawyer team at Dickinson Dees was led by company and commercial partner John Flynn.