Margaret Macmillan House was assessed for designation as a Listed Building in 2023. It was decided not to designate the building. From the Historic England designation report:

"The Margaret McMillan House, Wrotham, Kent, conceived as a memorial to the educational pioneer Margaret McMillan (1860-1931), was not a strictly educational site, having been built in 1935-1936 to provide a holiday home for children from the Nursery at Deptford, established in 1914 by McMillan and her sister Rachel McMillan, and the associated Camp School; the complex was also intended to serve as a residential training college for nursery teachers, gaining experience with the children. The institution was designed and run on the ‘open-air’ educational principles the McMillans had embraced. The site is therefore an interesting and unusual one, with each of its functions demanding careful consideration both separately and in combination.

A number of surviving examples of open-air schools have been listed, taking into account their different claims to historic and architectural interest. The buildings of the early open-air schools were generally very simple, with existing buildings being adapted and huts erected of timber or other materials. These fragile earliest buildings have almost all been lost, though the later timber pavilions at the LCC’s 1925 Aspen House do survive, and are listed at Grade II. England’s earliest surviving purpose-built open-air school, Uffculme School, Birmingham (1911, listed at Grade II) was brick-built and architect-designed, Barry Peacock producing staggered pavilion classrooms, opening completely on three sides. His innovative configuration provided a starting point for the later development of open-air school architecture; the listed Joicey Road School in Gateshead follows the design closely. Stylistically, the influence of the Modern Movement produced notable open-air schools on the Continent, but was rarely seen in England; Sir Hubert Bennett’s Swinton and
Pendlebury 1938 school in Lancashire has been demolished, but Newman School in Rotherham, built by the local authority architect Geoffrey Raven in 1939, which re-works the by-then traditional pavilion classrooms with their full-height glazed screens as a complex of flat-roofed structures in the International Style, is listed at Grade II.

Seen within the wider context of the open-air movement, the buildings of Margaret McMillan House do not stand out in terms of early date, innovative planning, or style. By the mid-1930s, the main period for open-air schooling was nearing its end, though its influence would continue to be felt on mainstream school architecture and approaches. The layout of the Wrotham buildings follows the open, linear plan dictated by the desire for through ventilation and dual aspect interiors which is typical of educational buildings by this date, not just open-air school design. The modest neo-Georgian style of the buildings, too, is typical of the period; the examples under consideration are nicely detailed and well suited to the rural situation, the formality of the open courtyard, and the requirement for simplicity.

The buildings at Margaret McMillan House survive well enough to illustrate their original purpose, but there have been some significant alterations. The overall footprint of the principal building is largely intact, with some small additions, whilst much of the original plan and circulation can still be understood, with the help of contemporary plans. The covered way, linking the various parts of the site, remains legible as a planning element, despite the sides having been filled with uPVC; the fact that this has been blocked in two places to create new rooms perhaps has more impact. The large dining and play room is the interior that survives best, retaining the majority of the large windows and folding glazed doors which surround it on three sides, though some have been lost or modified; the timber roof structure remains open above. The other particularly significant rooms – the boys’ and girls’ sleeping shelters – have been subdivided, with the space formerly occupied by the girls’ dormitory being completely altered. Whilst many of the building’s original timber windows and folding doors do survive, there has also been significant replacement in uPVC, including to all
the dormer windows at the front and all the rear windows; alterations and window replacement at the south end of the west wing (formerly the boys’ sleeping shelter) are particularly detrimental to the building’s architectural effect. The staff house continues to play its part in the architectural composition, but has seen some alterations, and does not retain features of interest internally. The students’ accommodation block, first built only slightly after the main buildings, in 1937/8, was extended southwards and upwards in 2008 as well as being completely refurbished internally; the resulting building somewhat overwhelms the main block and staff house, detracting from the integrity of the site. The inclusion of a historic barn as part of the original configuration, the building having been moved from elsewhere and adapted to make an additional play room, is an interesting feature; this later role adds a layer of historic interest to the listed barn.

The commemorative aspect of Margaret McMillan House is of interest, both for the recognition paid to Margaret McMillan and her work, and as a posthumous extension of that work by those associated with her, but this interest is not so strong as if McMillan herself had been directly involved in the site’s creation or design. Whilst McMillan was said to have dreamed of a house in the country for the Deptford children, her own great work was in the city. The well-mannered neo-Georgian buildings at Wrotham do not directly embody McMillan’s own frequently cited view that cheap shelters were the type of building best suited to her educational approach – though at this date, more permanent brick-built structures were generally used even for open-air schools. The association of Margaret McMillan House with the politician Nancy Astor, who was closely involved in its establishment, and the association with members of the royal family, lend interest to the story of the site, but these connections do not amount to special historic interest. Margaret McMillan’s work is recognised on the National Heritage List for England by the inclusion of the Margaret McMillan Nursery, and
also by the separately-listed 1932 memorial to Margaret McMillan at the school. Both sisters are
commemorated by a blue plaque at their former home in Bromley.

Historic England, 2023, Designation Report: Margaret MacMillan House (Unpublished document). SKE55506.