A contract to build two concrete bunkers with walls almost 6ft thick has been won by a Sussex building firm.

Adenstar Developments will build the bunkers at the oncology department of the Royal Sussex County Hospital in Brighton to house linear accelerator machines for the treatment of cancer.

The contract is worth £1.4 million.

The 5ft 6in walls and ceilings are necessary to prevent the harmful radiation produced by the medical equipment from leaking out.

In parts of the construction, concrete with special aggregates that costs eight times the price of normal concrete is used.

It is so heavy that the ready-mix lorries that normally carry six cubic metres will only be able to carry half their usual load.

The roof slabs have to be cast in single piece, requiring the contents of more than 100 lorries.

Derek Chapman, managing director of Portslade-based Adenstar, said the job posed no problem as the firm recently carried out an even bigger pour of concrete over a 12-hour period at Brighton Marina.