The plant has agreed to supply a total of 4,500 tonnes of steel to structural contractor William Hare. It will be used in the construction of the 40-storey office tower at 100 Bishopsgate and the 36-storey "Scalpel" tower at 52 Lime Street.
British Steel was launched on 1 June after it was purchased from Tata Steel by the turnaround specialist Greybull Capital. The Indian conglomerate put it up for sale amid an ongoing crisis in the industry, which was brought about by a global oversupply of steel and dumping by China.
British Steel’s commercial director, Peter Hogg, said that the market for steel used in construction is "highly competitive so to be working in partnership with William Hare can only be good for both businesses".
"The construction market can be very demanding and William Hare, and in turn our clients, demand all the materials we use meet the highest specifications," David Hodgkiss OBE, William Hare’s chief executive, added.
"It is also pleasing to be able to support UK manufacturing, however the main reason we are using British Steel is because of the quality of the steel they manufacture."