Developers Edge and Mitsubishi Estate have secured the funding package to push ahead with a £150m office overhaul of 125 Shaftesbury Avenue in West London.

Sir Robert McAlpine is understood to be in line to deliver the big revamp job, which is being taken forward on a speculative basis.

The funding deal clears the way for construction to start early this year after enabling works contractor John F Hunt completes site strip-out.

A consortium of Japanese equity investors – including Tokyo Tatemono, Toko Electrical Construction and Fuyo General Lease – alongside development finance from Sumitomo Mitsui Trust Bank are funding the EDGE Shaftesbury scheme.

The project already has planning to transform the dated 1980s block into around 250,000 sq ft of modern workspace, with a reworked entrance on Charing Cross Road and new rooftop terraces. Completion is targeted for 2028.

A key feature of the scheme is its low-carbon approach, with around 75% of the existing structure retained to reduce embodied carbon.

The refurbishment will increase the building’s height from 11 to 13 storeys and deliver new ground-floor workspace.

Fons van Dorst, managing director UK at Edge, said: “Securing this funding marks an important moment for EDGE Shaftesbury and for our partnership with Mitsubishi Estate London.

“We are pleased to move into the delivery phase and look forward to creating a building that serves its occupiers, its neighbours and the wider city for many years to come.”