The race to bring a 20-year-old building in the City of London up to date has narrowed down to between Multiplex and Mace.

Sir Robert McAlpine was also thought to be looking at the job but the familiar rivals for work in the Square Mile have now been left to battle it out.

Designed by Squire & Partners, the job at 65 Gresham Street for JP Morgan Asset Management is being described as one of the largest building reuse projects in the Square Mile.

Outdoor workspace will be added to every floor of the refurbished building

The building was originally designed by Sheppard Robson and completed in 2001 but the new plans involve expanding it from 24,995 sq m to 37,767 sq m. The proposals include adding balconies, upper level amenity space and outdoor workspace to every floor.

The last of the building’s seven major tenants is set to move out next summer.

Others working on the deal include cost consultant Turner & Townsend Alinea, project manager Opera, structural engineer Buro Happold, services engineer Atelier 10 and facade engineer Murphy Facade Studio.