Architecture: Final vision of a maverick draughtsman: Sir James Stirling's last great project was as powerful and imaginative as ever. Shortly before he died, he invited Richard Bryant to Germany for a guided tour

FOR ME, an architectural world without Jim Stirling, who died last week, is a depressing one. I first met him when visiting the Cambridge History Library with a group of fellow architectural students. This chance meeting led to an unforgettable guided tour into a world of spatial impressions the like of which I had not experienced before.

At the time I had no idea that I would become an architectural photographer, let alone that Stirling and I would form a professional relationship that would endure until our final meeting - by arrangement this time - in Melsungen, Germany, only weeks ago.

The latest project completed by Stirling, Wilford and Nageli is a production and distribution plant for B Braun, a medical equipment manufacturer, in a green valley site in the German countryside, about 10 kilometres (six miles) south of Kassel. It consists of an extraordinary collection of individual buildings each with its own strong personality, but choreographed in the landscape to form a distinctly lively, yet cohesive whole.

The approach from the centre of Melsungen reveals the complex as an architectural dam spanning the bottom of a valley. Seen from a distance, the various parts of the building are like perfect fragments of some latter-day walled city.

A wooden corridor runs in front of the gridded and textured concrete retaining wall like part of the fortifications. The timber struts that support it are of various lengths and set at what appear to be random angles; this gives the impression that the struts are legs and the whole corridor is alive and walking in front of the factory behind. It is a wonderful trick.

Behind the wall, none of the individual buildings disappoints and each is strong in form and character; the sophisticated reptilian office block, for example, contrasting with the raw, brutal quality of the production areas. Two dramatic concrete drums - a pair of giant architectural abstracts - conceal the ramps of the car-park which sucks in and spits out cars like the balls of some giant pin- ball machine.

Melsungen is meticulously presented tectonic theatre and its many architectural layers exhibit an imaginative and well executed attention to detail.

Discipline underpins the high drama - storage and distribution buildings make up most of the complex and these have been designed for expansion should production levels increase.

The site is a paradise for an architectural photographer.

The materials - concrete, wood and block-work - offer contrasting finishes. And there is diversity in colour and texture: concrete washed in a surprising magenta blue and the beautiful green of oxidised copper cladding.

Stirling always seemed to work better and more happily in Germany than in Britain where his powerful work was seen as an affront rather than as imaginative.

When I first arrived at Melsungen at night, I found Stirling ambling around the site with a small camera around his neck and, typically, the rest of his belongings stuffed unceremoniously into a plastic bag.

He photographed the buildings while I recovered from my high-speed autobahn trip from Bonn.

As Stirling snapped, a group of Germans arrived for a tour and the guide asked if the architect might like to say a few words. His short address simply diverted any praise to his German partner, Walter Nageli, and that was that: Stirling's exuberance was reserved for his architecture; he was not a natural public speaker.

Although I am a custodian of photographs by the late Richard Einzig, which include most of Stirling's early hard-edged buildings - the Cambridge History Library among them - the first building that I photographed for him was the Staatsgalerie in Stuttgart in 1984.

This must have been the highlight for Jim Stirling and Michael Wilford as a creative partnership, as it was for me as a photographer; the richness of forms and spaces, the generous and imaginative circulation routes all excited me greatly. Stirling's clients expressed great pride in their building and their enthusiasm was infectious.

My visits to Stirling buildings from then on always lasted several days, if not a week or two, enabling me to become familiar with the designs and to capture them on film in a way that pleased us both.

Stirling was no prima donna about the way he wanted his buildings photographed. He liked to discuss the approach in detail, but always ended up saying 'Well, you do what you want'. Our routine rarely changed; he was the perfect client. I hope his clients at Melsungen find something close to perfection in his last great building.

I have had the good fortune to photograph many of the best new buildings around the world in the past decade, but few have had the spatial and formal power of Stirling's. I have found myself becoming emotionally involved with them and the thought that there will be no more for me to photograph, I find a very sad one.

(Photograph omitted)