Multi-storey car park, 1968-70 by Michael Blampied and Partners for Debenhams.

The Welbeck Street car park, 1968-70 by Michael Blampied and Partners, is not listed for the following principal reasons: * Architectural interest: the extremely striking and well-designed structural screen to the car parking floors is compromised by the weaker ground-floor arcade which lacks the refinement in the design of the supporting columns; * Aesthetic interest: the Pop art inspired façade is derivative and is a relatively late example of the artistic style applied to architecture; * Planning: the split-level deck system for car parking was, by the late 1960s, a long-established model; * Technological innovation: the design of the individual modular units is accomplished – they dispel rainwater and tessellate to create a textural and jazzy façade – but the structural system had been pioneered by Seifert and Partners much earlier in the decade, and is exemplified, with greater architectural quality in Centre Point and Space House.

In the 1960s Debenhams department stores planned a new, flagship store on London’s Oxford Street. Westminster Council’s planning regulations at that time required such schemes to provide parking facilities, hence, a car park was commissioned behind the new shop and opposite the head offices, occupying a plot facing onto Welbeck Street, Henrietta Place and Marylebone Lane.

The brief was for a car park for c400 cars, storage for the department store and lettable space. Michael Blampied and Partners won the commission; the firm had undertaken many large scale commercial and residential schemes during the 1960s, in Britain and abroad. The new department store was built concurrently, to the designs of Adrian V Montagu and Partners.

The site, a somewhat awkward wedge shape, inclines towards Marylebone Lane, and a split-level design with ramp access was deemed the most suitable, though other arrangements were investigated. Split-level parking was, by this period, already an established form. Structurally, the building has a central spinal stack containing a lift and staircase, and external load-bearing walls of precast concrete V-shaped interlocking modular units. These support reinforced concrete beam and plank floors and negate the need for internal columns, providing uninterrupted parking decks facilitating easy manoeuvring and clear lines of sight.

Tessellated unit construction was well-established by the time the car park was built, though in this instance furthers the interest of modular construction through the creation of the complex, faceted units. Full-scale polystyrene mock-ups were produced and exposed to the elements for protracted periods to assess their weathering performance; their design was refined to dispel water effectively in order to minimise staining. The intention to express the structural form of the building was key within the design process, the break in the south elevation with the brick spine wall expresses the split-level form of the interior, neatly dividing the façade and using a combination of materials typical of the period.

Unlike the department store, Blampied’s car park attracted coverage by the architectural press. In a comparison of three car parking schemes, the Architects' Journal (1971) commended the successful approach. ‘Building’ (1971) reported that it ‘expresses both the function and the construction in a dynamic and visually exciting structure’ and that the development should do much for the tarnished image of car parking buildings generally, which, during the period were built in vast numbers but exhibited, generally, a dearth of architectural quality. In opposition to this, Blampied's design put aesthetic quality and structural ingenuity on a par with functionality creating a striking yet eminently practical building.

From the outset the facility was under used. Westminster’s statutory undertaking for car parking as a condition of new development was bolstered by the 1963 Buchanan report, ‘Traffic in Towns’, published by the Ministry of Transport, which advocated urban multi-storey car parking. However, as stated in the Architects' Journal, motorists were not yet educated in using car parking buildings, preferring on street parking. It is suggested that only further on-street parking restrictions would increase use. The lack of a ‘reservoir’ in which cars could queue for entry would have resulted in traffic jams on Marylebone Lane, had customers been more numerous. The car park has remained in use since it opened in 1970, though custom remains low owing to Central London’s traffic restrictions and the good provision of public transport.

The lettable units have undergone alteration to suit changing occupants. In the basement was a large refrigerated stock room for storage of furs; this was in use for a limited period as tastes in fashion changed. A subterranean linking tunnel to Debenhams head offices at No. 1 Welbeck Street remains extant.

Multi-storey car park, 1968-70 by Michael Blampied and Partners for Debenhams.

STRUCTURE AND MATERIALS: load-bearing pre-cast reinforced concrete units forming the external walls, reinforced concrete floors, and brick spine wall and stair and lift towers.

PLAN: the building occupies a wedge-shaped plot bounded by Welbeck Street to the east, Henrietta Place to the south and Marylebone Lane to the west. Debenhams head offices are directly east, and the department store to the south.

It has a split-level plan of nine storeys plus a parking deck on the roof, and a basement.

EXTERIOR: the upper storeys each have a row of faceted V-shaped modular concrete units that interlock with the row above; modified units are used at junctions, as a parapet and to turn corners, ensuring the continuation of the pattern and producing highly geometric facades. The Irish Millwhite aggregate in the concrete produces its pale colour. On the south elevation there is a brick tower that divides the elevation and expresses the change of internal levels. Brick towers are used at the junctions with the buildings to the north and hold fire escape staircases.

The double-height ground floor has square posts supporting arched beams that form a fascia, behind which are the fronts of the commercial units along the south side of the building. Walls have porthole windows and are rendered with shaped panels. On either side of the building to the north are vehicular entrances to the parking decks, and secondary entrances to the commercial units and basement. There is mosaic detailing in some ground floor bays.

INTERIOR: parking decks are uninterrupted open spaces with two ramps at the north and south sides providing ascending and descending routes for cars. Decks are lit naturally with light penetrating the modular units of the elevations, and with strip lights. The original bumper rails generally have been replaced by timber planks; additional metal barriers have been installed throughout, these are not of special interest. Original signage on plastic panels, some backlit, survives.

The interiors of the commercial units have been adapted and modified as their use has changed. The basement remains as when built, with a large, lined refrigeration room, ancillary storage areas and bays for window dressing exercises.