In the height of the cold war, back in the days when our foes were defined and known and telephones had wires attached, the post office built a bomb proof telephone exchange on the banks of the Thames, between Cannon Street station and London Bridge. Its concrete is clad in GRP (glass reinforced polyester), bright even after 30 years exposed to the elements. With the windows presenting a dark contrasting surface, it's no shrinking violet. Deep in its subsurface heart, lurks giant generators to power the building in the event of attack from the enemy, evidenced by the huge cooling cubes on the roof of the building.

Designed by architects Hubbard, Ford and Partners, on its completion in 1975 Mondial House was the largest exchange in Europe. The striking stepped-back style allows unobstructed views of St Paul's Cathedral beyond in line with strict planning requirements for the area. The front of the building facing Upper Thames Street, incorporates its name in the concrete that surrounds the building, and also the fire station that sits under one corner.

If anything should be deemed to entitle a building to special protection, it's a slating from Prince Charles, describing it as "the dreadful Mondial House". "To me, this building is redolent of a word processor," he wrote, apparently as criticism. To me, it's more like the seminal Commodore PET computer, but that's a semantic difference - either way, Mondial House is a bold, striking, innovative building.