London's new concrete hall complex on the South Bank of the Thames was designed with the basic assumption that all exposed concrete would have a prominently board-marked finish. The result is an architectural feature of exceptional beauty. Considerable research, and great care during construction, were necessary to achieve the final effect. When contractors were invited to bid for the job, they were shown a sample panel at the site. This, they were told, is the standard against which all the concrete finishes throughout the job will be judged. Under the terms of the contract, the contractor was then obliged to construct a panel for comparison purposes which was designed to meet all the contingencies likely to arise during the actual construction. This trial run allowed finishing problems to be solved inexpensively before the main operations began. Formwork of rip sawn Baltic pine was found to give the most satisfactory grain structure to the cast concrete. Boards of varying thickness were used to give a more pronounced vertical patterning. Special care was necessary, however, to ensure that boards at construction joints were on the same plane. Polyurethane strips proved to be valuable for avoiding grout spillage at joints. The exposed concrete throughout the complex was finally washed down with a weak solution of hydrochloric acid to remove calcium deposits. A silicone finish was applied externally for weather protection.