34 Portland Place & 73 New Cavendish Street, London

The project is unusual in having to accommodate formal diplomatic representation, private residential life, working offices and public-facing cultural activity within the same connected estate. That affects almost every discipline. Security, fire strategy and circulation must distinguish public, staff, guest and private areas. The representative spaces at 34 Portland Place must retain the architectural formality of the historic house while functioning for contemporary diplomatic events, while the Cultural Institute at 73 New Cavendish Street must accommodate public engagement, exhibitions and multifunctional uses while sharing infrastructure with secure diplomatic functions. The design therefore needs to work at both ceremonial and everyday scales.

At 34 Portland Place, a major objective is to recover the legibility and hierarchy of the original townhouse. The proposals include the reinstatement of principal rooms, removal of unsympathetic later subdivisions, recovery of historic openings and improvement of the relationship between principal and subsidiary spaces. A Georgian enfilade is being restored, individual principal rooms are being returned to their original proportions and lost architectural details are being reconsidered using documentary evidence. The project also proposes a historically appropriate fireplace where one had been entirely removed and the reinstatement of an Adam-style ceiling for which archival evidence survives. The objective is not stylistic reproduction for its own sake. It is to restore architectural hierarchy where evidence makes that restoration defensible.

Fire engineering is among the project's most important considerations. The historic means of escape link 34 Portland Place and 73 New Cavendish Street with 36 Portland Place, so life safety, neighbouring interests including a school, and sequencing extend across three buildings of varying ages, typologies and ownership. Attention to detail is therefore paramount. All the buildings are also listed and subject to various deeds, historic private agreements between interest groups and trustee oversight - you get the picture. Our job is to communicate why the upgrades are vital, why they bring cumulative benefits and why it's worth investing now to secure a safer future. This necessitated close coordination between the fire engineers, Freeholder, design team, structural and MEP engineers, Building Control, neighbouring tenants and the adjoining property's fire advisers, alongside multiple planning and Listed Building Consent consultees.

The Howard de Walden Estate is one of the most important great estates in London and in this case the Freeholder of the site and many of the adjoining neighbours, so a separate Licence to Alter process sits alongside the Westminster planning and Listed Building Consent process. Cohanim has been coordinating information - architectural drawings, fire and means-of-escape information, technical proposals and matters affecting adjoining properties - so that statutory and Freeholder reviews can progress in parallel rather than sequentially. Freeholder review, board approval requirements and fire-safety review remain active project dependencies. Further to this, our team makes a point of building a sustainable and friendly relationship with the stakeholders, which is what has successfully transpired.

Given the age of the buildings, many substances can include hazardous materials, such as lead paint, among others. To carry out the work effectively and enable works to commence safely, scientific and health and safety investigations began during the earliest project stages. This involved working with, among others, Mark Womersley and Eton Group, along with several laboratories. Reviewing the historic project drawings often is incredibly valuable too - previous architectural sketches and drawings and site correspondence often yield surprisingly insightful information! This work has allowed hazardous materials, moisture, mould and existing-condition risks to be considered as part of the design rather than being left to the general contractor as a “site variation” - reducing risk for our client, contractors and all consultants.

Existing listed buildings rarely conform neatly to modern drawings, so structural design has developed alongside surveys, opening-up and continuing site verification. The Stage 4 work includes new and altered openings, local strengthening, riser interfaces, roof structures, lift shafts and pits, existing steelwork, basement interventions and the relationship of new services with historic structure. Many of these elements simultaneously engage heritage and Party Wall considerations. The project is consequently being designed iteratively: survey, model, inspect, coordinate, verify and then detail.

Existing services had reached the end of their operational life. A complete services strategy was therefore developed across mechanical, electrical, public health, lighting, fire alarm, security, suppression, gas, water and other associated systems. The design team has repeatedly reviewed service routes, perimeter zones, localised bulkheads and plant positions to protect ceiling heights in the principal spaces whilst developing a series of sensitive interventions that allow for site-wide upgrades to the services.

Inclusive access is another major part of the project. The wider strategy includes accessible WC provision, improved entrance arrangements and new lift infrastructure. At 73 New Cavendish Street, a new passenger lift is proposed within later fabric to provide substantially improved step-free circulation while reducing the impact upon significant historic material. Lift works have required their own coordination across structure, Party Wall considerations, Building Control, fire strategy and specialist lift design.