The news is a blow to the three firms bidding for the job – BAM Construct, Brookfield and Mace.

Work was due to start on site by the end of this year.

But Derwent has confirmed construction will not now start until 2015 after Saatchi’s parent company Publicis Group agreed a longer let on the building.

Derwent confirmed: “The start of the Group’s 385,000 sq ft (35,800 sq m) redevelopment of this property is now likely to commence in the first half of 2015 with completion scheduled for the second half of 2017.”