The redevelopment of the former Scottish Widows headquarters is on the horizon after a planning application was lodged for a £100 million redevelopment of the site.

Under the proposals, five of the famous 12 bronze glazed, hexagonal blocks which make up the building on Dalkeith Road would be demolished along with the large underground car park.

A total of 194 flats – 35 per cent of them affordable – would be built in five blocks up to seven-storeys high within a landscape setting on the rest of the site.

The application by global investment firm Schroders Capital and Edinburgh-based development management practice Corran Properties Limited, follows an comprehensive public that involved both in-person and virtual consultation events.

They say the existing building no longer meets the standard required of contemporary offices and has the lowest possible rating for environmental performance. But they say their proposals would bring the retained offices up to the highest environmental standard for modern working.

Originally designed in the early 1970s and opened in July 1976, the building has remained under the ownership of Scottish Widows, although the headquarters moved to its present building on Morrison Street in 1995.

Often attributed to the acclaimed Scottish architect Sir Basil Spence, the building’s design and development was actually undertaken by Spence’s partner, John Hardie Glover and senior assistant, John Marnoch Legge.

Nick Ball, from Corran Properties, said: “I would like to thank all those who took part in the pre-application consultation and shared their thoughts on our proposals and their memories of working in the building. We are taking a meticulous approach to its restoration and re-use, whilst ensuring that the site can be returned to a positive, sustainable and active use.

“We were delighted to open the building’s doors for our public exhibition earlier this summer, and as we move to this next stage, we look forward to continuing to work closely with key stakeholders and interested parties to bring forward this important project for Edinburgh.”

Guy Morgan, managing director of Morgan Architects, said the submission of the application marked the culmination of more than a year and a half of intensive work. “Our team has come to appreciate the huge technical challenges of this unique building alongside its expressive architectural qualities. The mixed-use proposals seek to utilise the latest innovative technologies and design practices to create a sustainable, desirable and inclusive scheme of the highest environmental standards whilst retaining and enhancing the key heritage characteristics of the original building and landscape setting”.

The proposed flats would be built in a landscape setting on the site.

Rebecca Gates, head of UK asset management for Schroders Capital’s Real Estate team, added: “Following the excellent public engagement at the consultation events, we are pleased to be submitting a planning application, that would result in this significant site being reinvented with sustainability at its core.”