HBG HAS beaten four others in the battle to build a new wing at the Natural History Museum.
The museum in South Kensington, west London, has started negotiations with the contractor for the construction of the Darwin Centre Phase Two.
Five firms had been battling it out for the £65 million job but HBG has been chosen as preferred bidder.
Those that failed to make it through the selection process were Laing O'Rourke, Mowlem, Sir Robert McAlpine and Skanska.
The first £20 million phase was completed by Shepherd five years ago and now houses the museum's 22 million animal specimens. The firm did not tender for the latest project as it decided it already had enough work in the capital.
The new eight-storey building, designed by Danish architect CF Moller, will house a collection of 28 million insects and six million plants, including those collected by botanist Charles Darwin. The specimens, some of which are 300 years old, are being stored in temporary accommodation in more than 140,000 drawers in 7,250 cabinets.
The 19,500 sq m Darwin Centre Two will be a concrete framed building with a glass exterior and is designed to open up the museum's collection to the public, the bulk of which was previously behind closed doors.
The collection had been housed in a 1930s building, but since regulations stopped the use of chemicals the building has been vulnerable to pests, which can damage the specimens. It will now be demolished to make way for the new bug-proof building.
Work is due to start next month and the complex should be open to the public by the winter of 2008.