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Sir Owen Williams: Pioneering British architect and engineer
Sir Owen Williams was one of 20th-Century Britain’s most influential engineering architects who left behind a rich legacy of innovative modernist buildings. On the 50th anniversary of his death in May 1969, we celebrate two of the iconic buildings he designed and which we have been privileged to advise on, helping to secure their future. 1912: Enterprise House, Hillingdon (Grade II listed) Enterprise House is an early and innovative example of a reinforced concrete framed industrial building. Built for the Gramophone Company at its Hayes headquarters in 1912, the building was designed by Owen Williams in conjunction with Arthur Blomfield and A. Henderson, who – unusually, for this date – used the Kahn system of reinforcement and expressed the structure of the building externally. It is the earliest known work of Owen Williams, and it joined a growing collection of Gramophone Company buildings at the beginning and middle of the 20th Century designed to meet the needs of the records factory. Enterprise House is thought to be the first complete building by Truscon (the “Trussed Concrete Steel Company”). The Kahn system utilised ribbed reinforcement, a Kahn bar, with a square section featuring two projecting strips on opposite corners, bent upwards at angles to provide additional reinforcement to counteract shear stresses. This was a revolutionary new system used initially in the United States for factory buildings built around “daylight factory” principles to provide large expanses of natural light for factory workers. Enterprise House utilised the Kahn system in a very successful way, with form following function: the structure was externally expressed in a striking design aesthetic, not concealed behind brick or render. The result was a building which is highly evocative of the early 20th Century. The experimental nature of the construction materials and methods meant that, by the beginning of the 21st Century, rusting reinforcement and serious concrete deterioration required urgent and radical steps to conserve the building. Together with the then owners and an experienced team of architects and engineers including FSP Architects & Engineers, Furness Partnership and Furness Green Partnership, we worked to develop proposals for the complete refurbishment of the Grade II-listed building for mixed uses, including a factory producing vinyl records, a business centre, a café and residential units. Enterprise House is listed as a ‘Priority D’ structure on Historic England’s 2018 Heritage At Risk Register, recognising that a solution has been agreed but not yet implemented. It is hoped that once implemented the works will allow it to be removed from the Heritage At Risk register. Enterprise House is situated opposite The Old Vinyl Factory (formerly known as the EMI/HMV site), which is being redeveloped as part of a project to reinvigorate the former industrial area. As Planning Project Manager for The Old Vinyl Factory development site, we devised a planning strategy for the site. We successfully secured outline permission for a mixed-used redevelopment scheme including restoration of former factory buildings and conversion to accommodate over 600 residential units with additional workspace, helping to preserve and enhance the setting of Owen Williams’s earliest structure. In 2013 the masterplan and mixed-use redevelopment scheme for The Old Vinyl Factory was granted outline planning permission. The majority of the masterplan has now been approved in detail and some of the buildings have been completed and are now occupied, resulting in the Hayes Botwell: Thorn EMI Conservation Area being removed from Historic England’s Heritage at Risk register. Figure 1: Enterprise House is the earliest known work of Owen Williams; it is hoped that once implemented, the works will allow the building to be removed from the Heritage At Risk Register.    Figure 2: The Record Store by Wallis Gilbert and Partners (1927) forms part of the Botwell: Thorn EMI Conservation Area in which Owen Williams’ Enterprise House is situated. The conservation area has successfully been removed from the Heritage At Risk Register. 1951-55: British Overseas Airway Corporation Technical Block A (Grade II listed) Technical Block A (TBA) is a Grade II-listed hangar at Heathrow Airport, designed by Owen Williams and built between 1951 and 1955. TBA involved an innovative application of concrete engineering to aircraft hangar design: four hangars were centred on a triple-height engineering hall with offices for the former British Overseas Airway Company. The central spine features a stunning series of long-span reinforced concrete arches which provide an unusually wide and long—867 feet—space, formerly used for engineering workshops. The colossal structure was designed to house the entire corporation under a single roof, providing both cellular office accommodation and large, well-lit spaces in one building – a serious engineering challenge for its day. Originally designed for a 30-year lifespan, the building still continues to be an integral part of British Airways’ operations, though changes to the building have been necessary as the design and maintenance requirements for aircraft has changed during the 20th and 21st We carried out extensive historical research into the original design, which confirmed Owen Williams’s vision for a flexible building capable of evolving to meet the needs of the aviation industry. As part of the building’s evolution, we secured planning permission and listed building consent for the British Airways Global Learning Academy, incorporating flight simulators in the central engineering hall to train British Airways pilots. The result has been the reuse of a partially disused building, transforming it into a valued training centre as well as an operational aircraft maintenance depot, and ensuring the continued use of Owen William’s innovative aircraft hangar structure. Extensive discussion took place with Historic England and Hillingdon Borough Council to agree the acceptability of the works to the listed building. These included removal of a later 1960s set of offices which although not of special interest themselves, did illustrate the evolving functioning of the building in line with Owen William’s vision of creating a flexible space. The sixteen flight simulators together with their operational requirements such as operating offices, electrical requirements and maintenance rooms also had to be carefully incorporated within the building. The aim was to insert the pods along the length of the triple-height central engineering hall while still retaining views of the impressive concrete frame that spans the hangar. Lichfields’ heritage team, who are dual qualified members of the Royal Town Planning Institute and Institute of Historic Building Conservation, can provide assistance on listed buildings of all ages to assist with securing a sustainable future for an asset. Please contact the Heritage team on 0207 8374477.


Preparing Statements of Heritage Significance
Historic England (HE) recently published a consultation draft on preparing statements of heritage significance, setting out how the requirements of the National Planning Policy Framework (NPPF) can be met on that front.[1] While Historic England has previously produced a wide variety of guidance documents aimed at helping owners, occupiers and developers understand the significance of heritage assets, this consultation draft helpfully brings together both NPPF policy and HE guidance. The NPPF defines heritage significance as being ‘the value of a heritage asset to this and future generations because of its heritage interest’, which may be archaeological, architectural, artistic or historic. The HE consultation draft guidance adopts these terms, helpfully aligning with the NPPF terminology in lieu of ‘evidential, historical, aesthetic and communal’ values formerly referred to in HE’s Conservation Principles, Policies and Guidance (April 2008, currently under review). The draft guidance emphasises the importance of understanding heritage significance as a process separate from preparing the scheme proposals or designing out harm to significance. While this sequence is important, it also recognises that as designs develop and investigation works are carried out, an asset’s significance may be better revealed or understanding of it may change. Understanding significance is not a linear process, but it should form an important baseline. For Southbank Centre, a statement of significance and diagrams illustrating areas of importance formed key parts of the accessible conservation plan for the site. Proportionality in assessments is highlighted in the draft guidance: it notes the NPPF recognises that information on heritage assets should be proportionate to their importance and no more than is sufficient to understand the potential impact. The draft guidance helpfully explains that streamlined assessments are appropriate for straightforward cases, minimal impacts or changes to areas of the building of secondary or tertiary date and significance. Depending on the complexity of the asset and the proposals, a statement of significance and impact can form part of a covering letter or Design and Access Statement, or can comprise a detailed, stand-alone assessment. The draft guidance also touches on the methodology used to assess significance: it identifies that while sensitivity matrices and scoring systems can be useful quantitative tools, ultimately “significance and impact are matters of qualitative and expert judgment”. Any quantitative methods should be used in conjunction with a narrative argument identifying what contributes to significance, why it matters and how the proposal would affect the asset’s significance. Our statement of significance on West Horsley Place - a Grade I listed Tudor mansion - utilised both quantitative and qualitative methods of assessing the significance of the wider site. As practitioners, we agree with paragraph 6 of the draft guidance, which highlights that it is crucial for significance to be identified up front to save abortive work and cost. However, it is difficult to define a proportionate scope of assessment without having an initial scheme in which to respond. The process needs to be iterative and may require a staged approach to understanding significance, with more detailed assessment of significance carried out on areas where alterations are proposed. We note in paragraph 10 of the draft guidance that applicants are encouraged to agree the precise extent and nature of an assessment of significance with the local planning authority. While this is laudable best-practice, it is often unrealistic given the time constraints upon local planning authority conservation officers and difficulties getting in touch with them as a result. In addition, costs and time delays associated with pre-application consultation may mean that in practice, agreeing the scope of the assessment of significance with the conservation officer in advance may not always be practicable. When Historic England (as English Heritage) published Conservation Principles in 2008, this was a milestone in a qualitative approach to heritage significance. It encourages the practitioner to consider why an asset is important and this thinking has been incorporated into the NPPF.  However, the question of how to assess the scale of that significance (how important is the asset) has not been addressed in policy or guidance even though it is an essential consideration in the balancing process that is the planning system.  This new guidance stresses the need to identify the level of significance but leaves such evaluation to expert judgement. Given the difficulty in codifying such a process for the whole range of asset types this may be the most sane approach to take.   [1] Historic England: Guidance open for consultation