BAM Construct UK is to give a former government office block in central London a £23m upgrade.   The contractor has secured the deal to alter and extend 1 Page Street in Westminster for developer Derwent London.   The building was used as Westminster Hospital in the 1960s and more recently as a home for the Department for Environment, Food and Rural Affairs.   BAM will carry out extensive works to create 11,000 sq m of high quality, contemporary office space.   The scheme will include a steel frame extension, removal and disposal of the existing façade and replacing it with modern brick and punched windows.   New lifts, external works, and mechanical and electrical services will be provided, as well as raised floors and suspended ceilings.   Construction director Mike Donegan said: "I am extremely pleased that BAM has secured this important contract with Derwent London.   "The project will require a comprehensive reworking of the existing building, particularly given its historic uses.   "We look forward to creating the fantastic office space that this prime location deserves, and continuing our relationship with Derwent.   “The London commercial sector is beginning to improve after a difficult few years and BAM is proving that it is well placed to play a big role in its future."   BAM Construct completed a major refurbishment of the iconic Angel Building near King's Cross for Derwent last year and is about to complete a commercial scheme at Chiswick Green for sister firm BAM Properties.