Plans submitted by the AJ100 practice in August 2024 for Brookfield Properties envisage part-demolition, retrofit and an extension of the 1980s building at 60 Chiswell Street in the City of London. The sites floor area will increase from 24,800m to 39,000m.However, Milton Gates iconic castle-like form and green-glass faade would disappear as part of AHMMs plans for one of the last projects by Lasdun, best known for designing the National Theatre.Responding to the planning application, Historic England said in a letter dated 17 January that the bulk and scale of the proposed scheme would cause harm to several listed buildings in the Chiswell Street Conservation Area.AdvertisementThe governments heritage watchdog continued: The scheme proposes partial demolition, infilling, extension, and alterations to the existing building. As a result, the proposals would have a greater impact than the existing building.It said that the increased bulk and presence of the development on Chiswell Street would lead to the scheme diminishing the visibility of these heritage assets within the wider context of the City, including the 18th and 19th-century Brewery conference venue, which is part Grade II and II* listed.It also argued that the harm would be cumulative because of nearby projects including emerging SOM plans for a 21-storey development at 1 Silk Street and EPR Architects submitted scheme for an overhaul of the Brewery.While SOM is still to submit a detailed application, Historic England has separately issued serious concerns on heritage grounds over EPRs plans to add a roof extension to the former Whitbread Brewery building, according to a letter sent in December.Heritage campaign group the Twentieth Century Society applied to have Milton Gate listed in 2023 but the attempt was unsuccessful and a certificate of immunity (COI) from listing was issued not long after.AdvertisementHistoric England said it would not list the building because its glass faade was a style which had been used more successfully elsewhere and that the original interior atrium and entrance had changed significantly since the building was completed in the 80s.AHMM says its scheme would deliver refurbished Grade A office space while retaining most of the structure. Its plans include activated ground-floor uses, a new entrance, and improvements to energy performance.The practice has described the current castle-like design of Milton Gate as dark [and] defensive as well as being 'aesthetically dated'.The building was refurbished by Squire & Partners in 2007. It was soldfor 215 million in 2021 with AHMM appointed to the scheme following early involvement in the project by MCM Architects.AHMM and Brookfield Properties were contacted for comment.