Aukett Swanke Group said on Wednesday that the 326,000 sq ft Adelphi Building, on the north bank of the Thames in London's West End, had been fully let shortly after the completion of a five year phased refurbishment programme led by the company.
The AIM-traded firm said Blackstone, the developer, had successfully attracted high grade occupiers such as The Economist, relocating from their eponymous headquarters in St James; Conde Nast, Spotify and Shiseido to the building, which it said is a Grade II listed Art-Deco "landmark".
Appointed in 2012, Aukett Swanke's design for the first six floors was completed within six months from the project commencement in late 2015, the company said, followed by two further phases covering the upper levels of the building, all of which completed in April of this year.
The building was originally completed in 1938 to a design by architect Stanley Hamp, who was also involved in the nearby Savoy Hotel.
Aukett Swanke said the floor plan was "innovative" for its time and took the form of a 'double-E' shape, which provided setbacks to allow occupants to benefit from natural light and take advantage of the views over the river.
It said a key part of the appeal of the building to potential occupiers had been the provision of a modern workplace alongside the retention of the building's historic façade and classical features.
Aukett Swanke explained that its design ideas extended the setbacks down to draw natural light into the "deep space" on the lower levels of the building.
The practice also adopted the existing building's art deco themes with the detailing of dramatic new wall mounted reliefs in the reception area, the board said.
Additionally, the company said the creation of new ground floor restaurants and public realm as well as rooftop terraces completed the "broader appeal" to potential tenants, with most floors let to single occupiers.
"The Adelphi Building provides another high class example of the work that the practice is pre-eminent in. Aukett Swanke has extensive experience in converting listed buildings to new uses, thereby ensuring their continued viability in the modern world whilst retaining the outstanding historic architectural features," said Aukett Swanke Group CEO Nicholas Thompson.
"The new Four Seasons Hotel at Ten Trinity Square has been fashioned out of the former Port of London Authority Building in Tower Hill and, our long-standing involvement with the Grade I Listed Royal Exchange in the City of London has seen the building extended and modernised with new office, retail and restaurant use, ensuring the long term survival and popularity of this City landmark."