By virtue of paragraph(s) 3 of Part 1 of Schedule 12A of the Local Government Act 1972.
Information relating to the financial or business affairs of any particular person (including the authority holding that information).
The public interest in maintaining the exemption outweighs the public interest in disclosing the information because disclosure of the terms of the letting at this stage may result in the interest being lost. In addition, the terms contain financial information of the proposed tenant.