And now from the BBC …

On the other, it produced the grey hulk of a design-and-build office block overlooking the nearby Westway flyover. Now it is completing Allies & Morrison's £250m media village between these two sites. So which category does that fall into: inspired or drab?

Neither the site, the procurement route nor the client's brief for the media village were promising. As with the grey office block next door, it lies in the lee of the M40 flyover. It was procured by means of a 30-year PFI contract with developer Land Securities Trillium. And the brief was to house 3000 employees in 80,000 m2 of office space, some of which is to be used as "playout studios" where television recordings can be electronically edited and broadcast – but no studios for live broadcasts.

Allies & Morrison's masterplan won an architectural competition in 2000. At first sight, its masterplan is no more promising than the site or the brief. It shows a couple of new buildings lying parallel to the existing office block, all three with rectangular plans.

It is only when you visit the site that you are hit by the key attribute of this scheme: all three buildings are immense. Each is six storeys high and the size of a city block. The two new buildings are 100 m from end to end and each has a row of three internal atriums.

Although it may sound daunting, the unusually large scale of the buildings makes sense, both internally and externally. Graham Morrison, partner of Allies & Morrison, explains the internal logic: "There are four wings of office space 18 m wide separated by three atriums. So what you really have is four office buildings in a row. And as for the atriums, three is a good number because people know where they are in the building and everyone sits within 3 m of daylight."

The three atriums are connected by two internal streets that run through each floor from end to end. And the offices are largely open-plan, while the playout suites are set behind clear-glazed partitions. The combined effect is that, from the heart of the building, you can look all the way through to the perimeter glazing, and through that to the outside world. As Morrison puts it: "There's so much space in the building, it looks as if the layout is inefficient. But we've achieved an 86% ratio of net to gross floor areas."

The internal grid for partitions, ceiling panels and service runs has been offset from the 9 m square structural grid. As a result, the structural columns rise heroically as freestanding concrete cylinders through the the full height of the building. On a more practical note, the separation of structural and spatial grids helps the BBC to churn its office spaces, as partitions and services can be reconfigured without the structural columns and beams getting in the way.

The most prominent features in each atrium are a wide chunky staircase encased in natural timber boarding and, alongside it, rows of projecting sound-absorbent baffles, also in timber. "The staircases are a bit of an indulgence," admits Morrison. "They're located and sized so you can see people on them, and so that two people together can easily pass one person going in the opposite direction. That's because a lot of business is done on staircases, and we want to encourage that."

On plan, Allies & Morrison's street pattern looks unremarkable. Yet here again, visiting the buildings and intervening spaces and seeing how they interrelate in three dimensions tells a different story. "We've tried to make sense of a very damaged urban pattern," says Morrison, referring to the large site bounded by the huge 1980s office block, the Westway flyover and the 1930s White City council housing estate on three sides.

With this intention, Allies & Morrison has slipped in two narrow "perimeter blocks" between their large new office blocks and the council housing estate lying to the west. Though they contain office space and are quite contemporary in design, the perimeter blocks are long, three storeys high, have a regular rhythm of upright windows and are built of London stock brick, just like a traditional London terrace of houses. As such they provide a congenial buffer between the large, overtly commercial office buildings and the brick-and-pitched-roof council estate. Their presence has encouraged the council estate to clear out its defensive boundary of dense bushes and open itself up to the road between them for the first time. What's more, two open pedestrian routes leading past the perimeter blocks invite council tenants to venture into the heart of the media village.

Piazza-u-like
The main external space is an oblong one lying between the two new office blocks and the existing one. Surprisingly, this turns out to be a lively urban pedestrian piazza, thanks to a carefully considered combination of features. For a start, it has a satisfying sense of enclosure and containment. This is partly because its width of 30 m relates well to the height of the six-storey buildings on either side, and partly because it has been closed off at the north end by a reception wing that projects out from one of the new buildings, the Broadcast Centre.

Moreover, the ground floors of all three office buildings bounding the piazza have been taken up by social activities, made highly visible through window walls. In the new office building, the ground floor is occupied by a row of eight shops. Contrary to estate agents' assurances, they have all been let – to Starbucks and Tesco, among others – as they serve not just BBC staff but council tenants too. In the Broadcast Centre next door, an imposing double-height reception hall commands the head of the piazza, and a large airy cafe spreads out alongside it. Even in the ground floor of the existing office block, the tinted glazing to the staff restaurant has been extended and replaced by clear glazing facing out on to the piazza. As Morrison puts it:

"The ugly sister has at last been brought into the family."

On top of that, the piazza has been cleverly landscaped to match its role as a social hub. There are no amorphous clumps of shrubs and flowers. Instead, Christopher Bradley-Hole, winner of several garden design awards at the annual Chelsea Flower Show, has treated the whole piazza as a large outdoor work of architecture in its own right. He has divided it up into an orderly sequence of convivial rectangular open-air rooms with short strips of beech hedge, single semi-mature trees as punctuation points, low-level lighting, paving in Portland stone and granite, and plenty of solid park benches in stone and natural timber.

The two narrower outdoor spaces between the large new office blocks and the lower perimeter blocks have also been landscaped by Bradley-Hole. They are contemplative gardens with thick bamboo copses, extensive timber benches and a stream gurgling along through a central channel.

Auntie's modesty
As for the new buildings themselves, these are four-square blocks with well proportioned, neatly detailed facades in grey anodised aluminium and clear glass. The western and southern facades are fronted by projecting banks of louvred sunscreens. On the eastern facades overlooking the piazza, one-storey-height glazed panels alternate with narrow vertical strips of built-in louvres. In the office building, these are fresh air vents that can be operated by the occupants – whereas in the Broadcast Centre, which is air-conditioned, the louvre panels serve as emergency smoke vents.

Packing in some 80,000 m² of floor space, the BBC's new media village is big, but is also intentionally modest in design, as it accommodates business rather than public or cultural functions. "Our buildings are not like the proposed Music Centre," sums up Morrison. "They are well-mannered, calm and ordinary. You need a ground base of normality against which the Music Centre will stand as an iconic building. Otherwise you would just end up with an architectural zoo."

The big question is how well these buildings and the spaces between them enhance the working lives of the people occupying them. During Building's visit at the invitation of main contractor Bovis, project manager Richard Barnes was accosted by a member of BBC office staff, who said: "The building's great: all the staff are smiling." And the fact that the building is being fitted out to house the offices of the chairman and director-general does nothing to contradict this view.