Health and efficiency

If the contrast between a piece of architecture and its setting is strong enough, the results can be thrilling. In the deepest folds of Kent, at Benenden, there have been two thrills - one in 1937, and another this year. The two edifices in question are, very unusually, physically fused together in a fine example of joined-up thinking.

You have to get there first, though. And getting to Benenden is an important facet of the whole experience, because the buildings are in an unlikely, almost secret, slice of countryside. If you travel east from Royal Tunbridge Wells, the journey takes you toward Cranbrook, through prime hop-growing country. Shortly after Goudhurst - its parish church, the largely 17th-century St Mary's, is certainly worth a visit - you hang a right, then a left and another right. From there on, the motorist is poodling into a posh, gilt-edged back of beyond, where the houses seem to get bigger and more detached as the B2086 wanders eastward.

After 10 minutes, Benenden is attained. The precise object of our journey is a further five minutes north-east of the village, and when we reach it - the soft, dun hills rising protectively around us - the place seems quite impossible, some sort of stage set. Here is the 145-bed Benenden Hospital, established by the postal workers union in 1906, with its remarkable 1937 Lister Wing, a tuberculosis sanatorium for the "lower-funded".

The hospital is a medical anomaly - a trust paid for not by the health service but by several trade unions. It's also an eerie physical anomaly: the only thing missing is Patrick McGoohan in his piped blazer, a perma-glaring No 7 in search of No 1 in The Village of no escape. The place is swathed in rural bubble-wrap. On a sunny summer day, one looks up and expects to see a trio of ghostly Spitfires doing glinting victory rolls in the morning-glory-blue sky smudged with chalky clouds. Just imagine what the hospital's first consumptive patients must have thought when they pitched up and saw the gleaming Lister Wing. Was it a building, or a giant syringe-steriliser?

Today, we may look at it knowingly and think: pure, rigorous Modernism. Six decades ago, this building, designed by Burnet, Tait & Lorne, must have seemed as physically startling as the endoscopies that the patients endured.

But what an unexpected and physically charming building. Beautifully proportioned, utterly straightforward in plan and function, awash with light under a wafer-thin slab roof, with bedrooms looking south over a countryside whose beauty demands Vaughan Williams's Lark Ascending to emanate scratchily from the horn of a hospital Victrola. The Lister Wing, like those early TB treatments, was about hope, a better future - and experimentation.

In that respect, it was part and parcel of a clutch of significant Modernist buildings in that part of the south. Two others spring to mind: Wells Coates' Embassy Court apartment building in Hove, and the scintillatingly nonpareil De La Warr Pavilion at Bexhill on Sea, by Mendelsohn and Chermayeff. Tommy Tait chaired the jury that picked the pavilion's designers and must have known what a crucial precedent it would set for other architects who hoped to give severely elegant health-and-efficiency Modernism a foothold in Britain.

But the course of architecture never did run smooth; not in the long term, anyway. And so it was at Benenden. In the Fifties, the unions coughed up for an ultimately bungled attempt to double the size of the Lister Wing by duplicating it and attaching it to the original building, after knocking off one of its characteristic bull-nosed ends - a doltish idea, exacerbated by the fact that the new wing was not built to the same detailed specifications as the Lister.

Predictably, the so-called Williams Wing foundered. By the Nineties, leaking and with spalling brickwork, it had closed. Only the ground floor of the original Lister Wing was operational as a children's unit, and the hospital trust called in the architects John McAslan + Partners. The practice was tailor-made for the job. It had already restored and extended Frank Lloyd Wright's Florida Southern College campus and directed the makeover of Peter Jones department store in London, and was master-planning improvements to the De La Warr Pavilion. McAslan saw that there were two keys to designing a replacement for the Williams Wing, to be known as the Jubilee Wing. He had to restore the demolished bull-nose at the western end of the Lister Wing and come up with a new form that would not compete with the original. The practice has succeeded with a building whose simplicity entirely matches the Lister Wing in spirit.

The Jubilee Wing is set back behind a louvred metal façade, and the block is not, in itself, architecturally remarkable. But the layering of the two produces a much more notable effect, making the south elevation of McAslan's building both modernist and, fleetingly, baroque. The architectural commentator Ken Powell has suggested that the louvres hint at the spare but sophisticated "tin shed" designs of the great Australian architect Glenn Murcutt. The connection is tenuous: McAslan's façade feels substantial; Murcutt's buildings - and their sunscreens - are very delicately poised.

That's no criticism of McAslan's design, which had to be strong enough to balance the presence of the Lister Wing, but not too dramatically. The result is a new wing whose robust horizontal lines certainly draw the eye. The louvres do two things in particular: they more or less conceal the tidily arranged glass façade just behind them - a façade that would have looked plain if set, unobscured, next to the sweeping glazing of the Lister Wing. Second, the louvres reflect light, just like the original building.

Internally, McAslan + Partners have delivered a mix of treatment, consultation and service zones that is almost as simply arranged as in the Lister Wing. They've used colour, too - a deep, soothing blue in some of the common areas - and created a white stuccoed link building whose lines don't interfere greatly with the strongly horizontal flow of the two wings.

It is a job well done. And, with a price-tag of £2.8m for 1,858 sq m, it can be described as very good value. The Jubilee Wing's value, as architecture, is not that it's a completely ravishing building: it isn't, and couldn't have been at that cost. But it is a coolly conceived lesson in self-effacement - the kind of minimalism whose physical impact has been carefully weighted.

McAslan have made it look easy, when it could only have been fraught. Any failure with the proportions and detailing of the louvred façade would have undone the Jubilee Wing in an instant. Something old, something new, something borrowed, something blue. Benenden Hospital had one great little building. Now, it's got two.

Driving away from Benenden, one is left wondering why so many new hospital developments are less than satisfying, both architecturally and clinically. Money, of course, is an issue; so are permutations of land-use and long-term strategy. But new hospitals that do seek to push the boundaries of clinical care and general atmosphere remain conspicuously rare. And their rarity will perhaps be accentuated by the Government's intention to develop a two-tier hospital system, which may fudge the issue of rigorous, modern design.

Benenden is a small triumph couched in rather unique circumstances. But at least two other hospital developments stick in the mind for innovation that drove the architecture into new realms.

Healthy hospital syndrome can be experienced in, for example, East Acton, London. There, Avanti Architects delivered the Central Middlesex Hospital's beautifully designed Acad ambulatory care and diagnostic centre. A key element of the new approach was the complete administrative separation of acute care and non- emergency treatment. In the latter case, the development of a one- or two-stop-shop system would supply consultation, diagnosis and day-case surgery. The Acad centre is the fruit at the end of that vine, and its growth was tortuous. "They had a back-of-the-envelope idea of how much it would cost," says Avanti's co-principal John Cooper. "They wanted it to be a public building that would have architectural quality externally and internally. We were pushed to provide a building that was significantly different from NHS architecture." British hospital design has in the past been what Cooper calls "the East Berlin of our architecture". There were also several hugely expensive "breakthrough" prototype hospitals whose obsolescence was built in; and, finally, bargain-basement cruciform structures that were intellectually bankrupt, cheap to build but clumsy and expensive to run: the NHS as yet another frayed end of the post-war command economy.

But properly innovative breakthroughs on a large scale need to be attempted. And the Norfolk and Norwich University Hospital is a prime example. Here, a very big building has - perhaps riskily - been based on a big architectural idea, and tied to the controversial private finance initiative.

The new hospital - one of the planned new wave of 22 regional hospitals - is not stunning architecture in any absolute sense. Yet there is no doubt that its architects, Anshen Dyer, have produced something special in terms of layout, clinical zoning and public space. That they did so in a sector typically stretched to physical and clinical breaking-point makes it a notable achievement. But no more notable, ultimately, than that unique clinical enclave in Benenden. Quality is the only issue worth discussing, and architecture is right at the heart of it.