HBG IS tipped to land a £20 million office development in the City of London.
Rivals have said the firm is the only one left talking to client UBS Triton Property Fund.
Kier, Sir Robert McAlpine and Skanska were all chasing the deal for Prince Rupert House on Queen Street, close to Mansion House underground station.
One project insider said: 'We are expecting a decision on this imminently.'
The client wants to boost the existing office space from 65,000 to 75,487 sq ft and to include space for shops, bars and restaurants.
The six-storey office block is in a conservation area and so the original facade will be retained. Existing offices behind it will be demolished to make way for state-of-the-art facilities designed by Rolfe Judde architects.
Work will start next May and is expected to last two years.