Morgan Sindall’s fit-out arm Overbury is lined-up for the job – dubbed Project Saturn – which industry experts Barbour ABI estimate is worth £300m plus.

The transformation of Citi Tower will create a “workplace for the future” incorporating the latest technology and the highest standards of environmental design.

The revamped tower will contain flexible work and collaboration spaces alongside well-being zones for employees.

Construction work is expected to complete by 2025.

David Livingstone, Citi’s EMEA CEO said: “Citi Tower is a significant investment in our people and our growing business in the UK and the broader EMEA region.”

Citi purchased the tower at 25 Canada Square in 2019. The decision to refurbish the building and bring it up to modern efficiency and environmental standards instead of demolishing the existing structure is expected to save the release of an estimated 100,000 tonnes of embodied carbon.

Yasmin Al Ani Spence, Director at architectural firm WilkinsonEyre, lead designer of the project, said: “Citi challenged us to make a 20-year-old tower compatible with its vision for the future of work.

“Our architectural interventions will hopefully inspire both staff and visitors to Citi. Well-being has been put at the heart of the project by introducing innovative collaboration spaces, enhanced connection, state-of-the-art amenities and impactful access to greenery, promoting biophilia.

“The internal layouts are anchored around a number of vertical villages, which break down the traditional floorplates and encourage inter-connection between levels, creating a stimulating and exciting place to work.”