The Ministry of Defence has appointed 15 law firms to a panel from which it will choose practices in the next five years to handle its PFI projects.
Dibb Lupton Alsop is the first firm to be assigned a job from the panel, which also includes Herbert Smith.
Dibbs will act for the MoD in drawing up a tender for the redevelopment of Chelsea barracks, where the Buckingham Palace guards are based.
The MoD procurement department publicly invited lawyers to apply to the panel last autumn and informed the successful firms last month that they had been appointed. It has carried out a similar procedure with financial advisers.
The 15 firms were selected on the basis of several criteria, including the resources they had available and their experience. The selectors also ensured a good geographical mix of firms.
Dibbs spokesman Michael Clark said the firm was expecting to work for the next 18 months on the Chelsea barracks project, after which a deal is expected to be signed.
The project involves tendering for a private sector consortium to rebuild the barracks or build on a new site within a five-mile radius of the City centre.
He said it had attracted over 100 expressions of interest from developers, largely because of the prime location of Chelsea barracks and the opportunity to use it for a more lucrative development.
Herbert Smith is acting for the MoD in a similar project to update the ministry's main headquarters in Whitehall, which under the public sector would have a capital cost of at least £175m.