Welcome to the Archello Podcast, architecture’s most visual podcast series. Listen as Archello's Paris-based Editor in Chief, Collin Anderson, sits down with architects to discuss their careers and projects. Each audio episode is accompanied by a rich visual storyboard which listeners can use to follow the discussion.
Introducing Helen Ensor, Director and Robin Dhar, former Chairman, at Donald Insall Associates
In this episode, Archello is in London with Helen Ensor, Director, and Robin Dhar, former Chairman, at Donald Insall Associates.
For over 65 years, this practice has been at the forefront of architectural conservation in the UK, known for preserving historic buildings while thoughtfully integrating modern updates. The firm’s portfolio includes iconic projects like the restoration of Windsor Castle after the 1992 fire and the rejuvenation of historic estates across the country.
Listen and scroll as the two describe their personal journeys, discuss some of the firm's standout conservation projects, as well as speak about the ways historic buildings can be rethought considering sustainability and material innovations.
Inside Donald Insall Associates' office in Marylebone, London
Located in Marylebone, central London, adjacent to Regent’s Park, Donald Insall Associates' office is housed in a building with a distinguished past. Originally built as a private townhouse and later serving as an embassy, the property was thoughtfully repurposed after the Second World War at a time when large residences were deemed economically unsustainable. This transformation required a careful intervention to modernize the building’s functionality while meticulously preserving its historic character.
Previously, the firm operated from several offices. The decision to consolidate into a single venue was a strategic move designed to reinforce the firm’s focus on heritage. As Dhar remarks, “We work almost exclusively on historic buildings and historic settings. We understand the language. It's what we do.” This commitment is well represented in the choice of the Marylebone building as the base for the firm’s conservation work.
On merging heritage with innovation
Founded in 1958 during post-war Britain, Donald Insall Associates emerged at a time when attitudes toward historic buildings were markedly different. In its early years, the brand focused on understanding buildings and helping clients adapt these structures to meet contemporary needs. As Dhar notes, “Buildings live just like people live. We all have to adapt,” a concept that is neatly encapsulated in founder Donald Insall’s book, Living Buildings.
The philosophy emphasizes that old buildings must be reinterpreted and given new life rather than preserved in stasis. According to Ensor, over the decades the brand has evolved to center on two foundational pillars: heritage consultancy and conservation combined with forward-thinking design. Today, the practice applies these principles not only to traditional historic structures but also to all kinds of buildings that benefit from adaptive reuse. With a growing awareness of environmental factors such as embodied carbon, the firm increasingly views the conservation process as an environmentally preferable alternative to demolition and new construction. This expanded focus reflects a commitment to helping clients maximize a building’s potential while ensuring sustainability and sensitivity to its historical context.
On reimagining a historic asylum into a new college in Oxford
One of the practice’s most ambitious and transformative ongoing projects is the conversion of a former lunatic asylum in Oxford—a site with a fascinating past dating back to the 1820s. This grade II listed structure, along with other listed buildings on the site, forms the oldest part of the National Health Service estate and continues to function as a psychiatric hospital. However, modern care standards differ significantly from those of the early 19th century, and the facility was determined as not fit for purpose.
Ensor highlights that the original institution was built for genteel patients who could contribute to their own care. Over time, as societal needs evolved, the building’s original purpose became obsolete. Today, the site is set to become Radcliffe College, the first new Oxford college in decades, developed through a joint venture between the National Health Service, Oxford University, and a private philanthropist. The project is a study in contrasts. The original building, with its extension from the 1870s and its rich architectural heritage, is being repurposed to serve modern educational needs. “It’s wildly complicated,” Ensor confesses, acknowledging the enormous challenges posed by reconciling a building’s historic fabric with contemporary standards of care and academic functionality.
The transformation required not only innovative design solutions but also sensitive engagement with a building steeped in history. As one team member quipped, every time they began a project like this, “you briefly become an expert in the history and development of county lunatic asylum architectural styles.” This research and understanding ensure that every adaptation is informed by the building’s past. By studying historical documents, architectural details, and the original functions of spaces, the team has been able to propose solutions that honor the building’s legacy while equipping it for a new life.
On reinventing the Royal Albert Hall’s iconic identity
Another landmark project that has defined the practice’s approach to conservation is the refurbishment of the Royal Albert Hall. This iconic venue, built in the mid-1800s and known for its grand architecture, demanded a delicate balance between preserving its storied past and meeting the rigorous demands of modern performance usage.
Dhar worked on the project for over a decade. One of the most memorable aspects of the refurbishment was the innovative design of a bespoke carpet. The Royal Albert Hall’s unique oval shape presented an unexpected challenge: ensuring that the carpet’s pile direction remained consistent around curved corridors. The solution was groundbreaking—a carpet that became the largest single repeat design in the world at the time. Utilizing cutting-edge computer and weaving technology, the team devised a method where the joins were always part of the same direction, so that the distinct color changes were integrated into the design without seams.
Beyond the technical feats, the refurbishment of the Royal Albert Hall was about reinvigorating a cultural institution. The project underscored the importance of maintaining a building’s historic language while introducing contemporary interventions. “We had to understand what was significant about the building, what made it unique, and then build on that,” explains Dhar.
On refurbishing Westminster Hall and Windsor Castle
The practice’s portfolio also includes some of the most challenging projects in the UK—those involving national heritage sites like Westminster Hall and Windsor Castle. Westminster Hall, the oldest part of the Palace of Westminster, is a testament to medieval craftsmanship and has witnessed centuries of British history. In recent years, extensive work was carried out to repair masonry, conserve timber, and upgrade the building’s infrastructure in response to both aging materials and the pressures of a changing climate.
Refurbishments included installing the Queen's Jubilee window, recladding the roof lantern, and rebuilding the fan vaulting to improve rainwater drainage. Interventions were carefully planned to respect the building’s heritage while addressing modern-day challenges.
Windsor Castle presented a different kind of challenge following a devastating fire. The dual impact of fire damage and subsequent water damage from firefighting efforts required a meticulous salvage operation. “It was a three-dimensional jigsaw,” says Dhar. The process involved recording and salvaging every piece of moulding and detailing, ensuring that when reassembled, the building’s original splendor could be restored. The work was not only technical but also emotional. “There’s a visceral horror that people feel as they see a cherished friend going through this terrible thing,” Ensor reflects, highlighting the human connection to these historic landmarks. The collaborative effort to restore Windsor Castle was guided by one overriding question: How do we honor the past while giving these monuments a future that resonates with today’s society?
On charting a new course for historic buildings
For Donald Insall Associates, sustainability is not merely an add-on but an integral part of the design process. Dhar explains, “Historic buildings breathe in a way modern ones don’t—they absorb moisture and need to release it.” This unique characteristic means that upgrading energy efficiency in older structures requires bespoke solutions that respect their materiality. The firm has embraced this challenge, recently publishing a net zero strategy report and appointing a new head of sustainability to drive further improvements. “We’re developing a sustainability toolkit which we’ll overlay onto all of our projects to ensure that we are continuously reducing our carbon footprint,” says Dhar. This toolkit is designed to address the unique energy performance challenges of historic buildings—from upgrading glazing systems to developing new cladding materials that allow the building to ‘breathe’ while minimizing energy loss.
Moreover, the practice is acutely aware of the broader environmental impact of its work. In conversations about sustainability, both Dhar and Ensor stress that conservation itself is an inherently sustainable activity. “It is about unlocking the potential of existing structures rather than demolishing them and starting afresh,” notes Dhar. Yet, they are also keenly aware that simply preserving a building is not enough; the intervention must also be forward-thinking. “We have to push forward on all of these things,” adds Ensor, citing examples of how innovative design solutions are now being applied to reduce embodied carbon in historic fabric while still allowing buildings to function optimally in today’s environment.
