HM Treasury has given the PFI the ultimate endorsement – by using it to transform its own Whitehall property. And by awarding the job to a premier league project team, it has proved that a public–private partnership doesn't have to mean cheapskate design
This must be the PFI project par excellence. The client and end user is the mighty Treasury – heart and brain of the British state and nerve centre of its PFI programme – and the project is the refurbishment of its grand Edwardian pile in Whitehall.

With such high stakes, the Treasury wisely awarded the PFI to what permanent secretary Sir Andrew Turnbull calls "premier league players". They include Stanhope, whose chairman Sir Stuart Lipton also chairs CABE, Foster and Partners and ubiquitous management contractor Bovis Lend Lease.

What the government has bought with its £170m, 35-year leaseback is not in the same lavish league as Portcullis House. Rather, it is an efficient, up-to-date office for civil servants, on a par with Stanhope's Chiswick Park – although in the solid masonry shell of a grade II*-listed building.

This transformation involved ripping out most of the warren of corridors, dingy cellular offices, multiple staircases and toilet blocks. In their place has emerged a clean-cut, open-plan modern office space to be shared by all staff – including the permanent secretary – although not the government ministers. The removed toilet blocks have made way for touch-down areas, equipped with counters and drinks dispensers. The colour scheme is generally white, with occasional splashes of vivid colour in the form of hanging banners.

Eight of the original lightwells have been smartened up and glazed over to provide communal spaces, such as training rooms. They also play a crucial role in a reborn natural ventilation system. Banks of louvres installed below the glazed roofs of the lightwells act as thermal chimneys, sucking air through the building and out of the overhauled timber sash windows.

The ground floor has been given over to communal spaces to encourage interaction between civil servants. These include a reception hall, restaurant, training areas and a tranquil landscaped garden.

The refurbishment of the half of the building facing St James's Park has been completed, increasing usable office space 25% to house 1200 Treasury staff. Work is now starting on the other half.

The Treasury building has been refurbished with that sure, fresh but unexorbitant touch that Stanhope and Foster and Partners can be relied upon to produce. So how has it escaped the design compromises so often associated with the PFI? According to project director Huw Thomas, the answer is simple: "At Foster and Partners, we don't take no for an answer."