The Abu Dhabi owner of 33 Cavendish Square in the West End has proposed a major refurbishment of the island site that could make it one of the most valuable buildings in London.

The building’s owner, the royal family of the Gulf state, has unveiled plans for a part refurbishment and part redevelopment that would create 800K SF of office space and about another 100K SF of retail and cultural space.

That would be one of the largest office buildings in the West End — 33 Cavendish Square is one of the few office towers in the district, and Westminster Council is unlikely to allow more in the vicinity.

Rents in the north of Oxford Street submarket have risen by 49%, and grade-A rents stand at £130 per SF, data from Devono showed. Putting a relatively conservative rent of £100 per SF on the building and an equally conservative yield of 5% would value the building at £1.6B before the retail was taken into account. It was bought for £433M in 2005.

The island site features a three-storey podium, part of which previously housed a BHS department store fronting on to Oxford Street, and the tract hosts three office buildings, the tallest of which is 21 storeys.

The podium will be demolished and replaced with new retail space and a cultural centre. The office buildings will be retained and reclad. Overall, 50% of the existing structure will be retained.

Berkeley Estate Asset Management, the building’s asset manager, and KPF, the architect, said that meant the project is in line with Westminster Council’s retrofit-first policy.

The team intends to submit a planning application later in the summer with the hope that it will be determined by early 2026.