PERHAPS I ought briefly to explain why I have volunteered to come this morning. It is primarily because for the last 45 years I have watched in despair as one remarkable industrial building after another has been systematically demolished to make way for what some people like to describe as "comprehensive redevelopment".

But these buildings are just as much part of our national heritage as cathedrals, palaces or country houses. Many were built to the highest architectural standards of their day and, despite the passage of time, remain in remarkably good condition.

We hear a lot these days about "joined-up" government. Well, I think it is most certainly time to talk about "joined-up" regeneration strategies. Too many regeneration initiatives have been undermined by short-term considerations which have favoured low-cost, new-build schemes and produced lots of breeze- block and tin factories or business parks, even in the heart of our most famous Victorian cities.

They have not taken sufficient account of the opportunities offered by heritage industrial buildings.

Policy-makers and developers too often make a presumption that "brown- field" sites mean "cleared and vacant sites". In reality, they frequently contain many reusable buildings that are often of striking architectural importance. They are a reusable resource and should be part of our drive to give practical expression to sustainability.

Given the fundamental shifts we have seen in our traditional economy, it is tempting for policy-makers to argue for the demolition of the old factories and communities. Then what? Are we to re-create the suburbs in the heart of our cities? Or perhaps whole cities are expected to move away to more prosperous areas in order to find work?

Surely a better way forward is to promote the process of re-inventing communities where people already live, and recognise the value of the investment both in people and the built environment that already exists, rather than abandon it.

After the last war, and right up to the Seventies, governments carried through an ambitious programme to build new towns. Millions were moved from congested cities to new and expanded towns with modern houses and workplaces. Lives were transformed for the better. But at a price. It took many years for communities to become established, and we have the phenomenon of "new town blues".

If we are to give meaning to any strategy of favouring brown-field development, there has to be an explicit recognition that much of the built environment, and especially heritage industrial buildings, represents a sustainable resource from past generations which is capable of being "recycled" for new uses.

We are accustomed to thinking of cities such as Bath and Edinburgh as places with a great architectural heritage, but visitors to Manchester, Glasgow and Newcastle are now, at last, beginning to recognise the beauty and value of our heritage from the industrial age. It is significant that the resident population of the city core in Manchester has risen from 400 to 6,000 in eight years - almost all living in converted warehouses and mills. Where a choice exists in favour of living in an exciting urban community, people will make it.

Regeneration strategies in the new millennium will also be operating in new economic circumstances. The world has moved into a new economic order - the knowledge-based economy. We need to create new kinds of communities where this economy can flourish - places where people will want to live and work, and will want simply to be.

I am not talking about the restoration of these buildings just because of their architecture, nor the creation of "Heritage Theme-Park Britain" where we repackage our heritage for the benefit of tourists. But there is no doubt that these buildings, and the environment in which they stand, can provide a uniquely attractive atmosphere for modern living and working. We need to rediscover the ingredients for such an atmosphere and try to emulate them in the future.

It was the great American urban historian, Lewis Mumford, who wrote that "If we would lay the foundation for a new urban life, we must first understand the historic nature of the city". As we wrestle with the regeneration of so many of our urban communities, finding successful new uses for remarkable old buildings is a very tangible way of retaining just such an understanding. When all is said and done, I believe we owe something to those craftsmen who built these buildings with such skill and pride.