HBG IS in line for a £95 million deal to redevelop the former headquarters of Marks & Spencer after the recovering retailer sold its central London offices.
Developer London & Regional Properties bought the long lease from Marks & Spencer for £115 million last year and is using it for one of the largest developments in London's West End.
Both the developer and HBG are remaining secretive about the scheme but project sources said the contractor was preparing to seal the deal.
The Baker Street office block was formerly known as Michael House. The building will be altered and renovated according to plans by architect Make, the practice of Swiss Re building designer Ken Shuttleworth.
The eight-storey building will be used mainly for offices and retail.
In the basement there will be parking and a health club with a swimming pool.
The planning application also includes 22 town houses at the back of the development, some of which have been set aside for affordable housing.
Marks & Spencer, which last week announced a 20 per cent rise in interim pre-tax profits, has been at the site since it was built in the 1957.
Last year the firm moved to a smaller base in Paddington, west London, after auctioning off its remaining desks, chairs and 60 mannequins.
Westminster City Council will decide in the next month whether to grant planning permission for the development.
But a previous planning application for a similar scheme at the site was passed for Marks & Spencer before it moved to Paddington.
Some internal demolition has already started and London & Regional Properties expects to be able to hand the property over to a new tenant in 2007.