As you think globally, you act locally; as I have tried to do in the Duchy of Cornwall's venture into the building of sustainable communities at Poundbury, near Dorchester in the South of England. And Here, I have been trying to put a certain money where my mouth is, or used to be, and to create a heritage for tomorrow.

Ladies and Gentlemen, I am most grateful to you for inviting me to help you celebrate the tenth anniversary of Edinburgh's achievement of World Heritage status. Back in 1989, in A Vision of Britain, I wrote that, in my estimation, Edinburgh was the most beautiful city in Britain. Edinburgh is, indeed, the remarkable result of the interaction of dramatic geography and history, high artistic, cultural and intellectual aspirations and well-directed economic endeavour.

In the 16th Century the High Street was regarded as a ‘grande place' of Europe. However, by the 18th Century “Auld Reekie” was bursting at the seams, without public buildings worthy of its status and ambition. Nevertheless, rather than obliterating the rich and complex tapestry of the Old Town, a New Town was built across the Nor' Loch. What we might call today “a new sustainable community”. It didn't seek to reinvent the wheel nor reject the past, but sought instead to complement it.

The construction of the New Town required vision and conviction. But the shared aspirations for the New Town were strong and clear from the start. The Convention of Royal Burghs in their, ‘Proposals for Public Works' of 1752, set out an ambition to, ‘improve and enlarge the city and to adorn it with public buildings which may be for the national benefit'.

There was also a powerful economic argument to the Proposals, which stated that, ‘The national advantages which a populous capital must necessarily produce are obvious. A great concourse of people brought within a small compass, occasions a much greater consumption than the same number would do dispersed over a wide country'.

It reads rather like an economic counter-argument to suburban sprawl! The City is facing some of the same pressures of development again today and it can only be hoped that such high ambitions will prevail over short-sighted commercialism in the newer parts of Edinburgh.

Ten years ago Edinburgh was granted World Heritage Status to safeguard the outstanding universal value of the Old and New Towns, as well as the Dean Village. However, to see this merely as a ‘protected area' would be rather missing the point. Far from erecting a cordon sanitaire around the centre of Edinburgh and retreating within it, its value as a living model of urban and architectural excellence could be, and indeed has been, regarded as a model for new development elsewhere, not just in Scotland but across the world, from the United States to Russia.

To view heritage as a living thing by finding new uses for old buildings and planning proactively in heritage areas has long been a concern of mine, and my own Regeneration Trust brings together two charities which have contributed to the rich heritage conversation in this country for some time: The Phoenix Trust and Regeneration through Heritage.

Edinburgh of course is a living organism, in a constant, dynamic process of sustenance, renewal and occasionally rejection. Because the majority of its buildings were built typologically, according to simple rules, with straightforward modes of construction, the city has proved flexible and adaptive. The City also demonstrates a proper valuing of the unique urban and architectural forms, and sustainable use of local materials that give Scottish towns and cities their distinctive character and which may help provide answers to some of the current pressures of managing growth responsibly.

This is not just a matter of architectural style, but of creating better communities. The Scottish Executive took a lead in acknowledging the importance of the built environment in 2001 by publishing its Policy on Architecture, and other groups in Scotland are also doing much good work in this area.

Some of those here today may possibly already be aware of the work of my Foundation for the Built Environment. It is one of 16 charities of which I am President, and which together comprise an effort to address the fundamental need for interconnectedness between the human and natural worlds.

The Foundation tries to promote design in a way that learns from the past and that enriches, rather than denigrates, human aspirations, while still meeting more basic needs. In our educational programmes for instance, as well as our project-based learning, and in partnership with others such as the Building Research Establishment, The Prince's Foundation is demonstrating that locally-derived settlement and building traditions and local materials reflect time-tested adaptation to place and indeed climate. This approach is now becoming of crucial importance as people begin to learn that it helps to provide a platform for meeting present day sustainability challenges. I am particularly keen, by the way, for my Foundation to play its part here in Scotland and I'm delighted that we have been able create a “Scottish Office” within it in order to concentrate on Scottish projects.

To achieve the delivery of these principles, an essential factor is, if at all possible, to allow those who will live in the community an opportunity to participate in the planning process for, as Patrick Geddes said, “town planning. . .must be folk-planning.”. With strong leadership, “many hands” can enrich rather than muddle the design. In order to engage the many parties needed to plan and build a place, the Foundation has pioneered a technique called Enquiry by Design, and this has been successfully employed in the setting out of a shared vision for both new communities and for managing and regenerating existing towns and neighbourhoods.

Underlying all of this is the much-misunderstood concept of tradition – often derided or neutralized into the term traditionalism. Traditionalism makes us forget how tradition really works; just as Modernism has blinded us to what it means to be truly modern. These terms encourage us to see tradition and modernity as enemies, whereas in any sane society they would surely be the best of friends - as was indeed the case in the relationship between the Old and New Towns.

Tradition, in truth, is not about style: it is about learning from the best of what has gone before. It is something infinitely varied, infinitely adaptable, infinitely changing – a language, even a dialect, that is based on a coherent grammar, allowing infinite flexibility and creativity within a discipline. Instead of locking ourselves in the province of the present moment, why shouldn't all of man's endeavours in architecture be considered as an open book – a vast repository of cumulative intelligence?

As you think globally, you act locally; as I have tried to do in the Duchy of Cornwall's venture into the building of sustainable communities at Poundbury, near Dorchester in the South of England. And Here, I have been trying to put a certain money where my mouth is, or used to be, and to create a heritage for tomorrow.

Now that over 1,200 people live there and 750 people work there, I hope that Poundbury, which was masterplanned by Leon Krier and developed by the Duchy of Cornwall under strict guidelines from the Treasury, is proving the point that it is possible to break the conventional mould of simplistically zoned development and create mixed-use communities.

Its lessons are simple: a network of legible, interconnected streets that accommodate the car while celebrating the pedestrian; the principle of encompassing work, play, shopping and living in a harmonious way within walkable distances and the “pepper-potting” of affordable housing and private housing – all the while attempting to restore a sense of harmony, proportion and, above all, beauty to day-to-day life. I was determined to show that you could mix affordable and private housing together.

Poundbury, of course, has its own genius loci, but the underlying principles can be a model with applicability elsewhere, as testified to, perhaps, by the large number of visitors from all over the world, themselves often involved in the planning of new communities. In the past two years, Scottish Business in the Community has brought over 100 visitors from Scotland to Poundbury – because, Ladies and Gentlemen, “Seeing is Believing”. There is no substitute for first-hand experience, I have discovered after the past 20 years!

While this is a contemporary example, is there really any need to look any further than this great city? Edinburgh has long been a model for inner city living. Back in 1989, when I was looking for an exemplar of good urbanism to show a group of senior developers, builders, financiers and professional consultants interested in urban design principles, it was to Edinburgh that I turned. I well remember what a revelation it was to the members of that group (some of whom are still working with my Foundation) to analyse how beautifully the city worked and examine such an eloquent demonstration of building communities on a human scale.

The New Town of Edinburgh also shows that a positive framework for development, or design code, can channel the creativity of many different architects towards an overall sense of harmony. The handsome cohesiveness of its terraces, without monotony, is to be contrasted to the cloned houses that we are today churning out like sausages in great volumes. I hear that a large new part of the Edinburgh waterfront, master-planned by the latter day Robert Adam, is to employ urban codes to achieve such a rich urban grain with the help of many different architects.

So Ladies and Gentlemen, the purpose of this conference is to celebrate the World Heritage Status of Edinburgh and address the challenges facing it. However, this should also be seen in the wider context of Scotland as an interconnected whole. Other towns and cities in Scotland face many of the same challenges, and indeed many of the issues are interdependent. Glasgow, perhaps Corinth to Edinburgh's Athens, with its own distinctive urbanism and architectural masterpieces, including the World Monuments Fund-listed St Vincent's Street Church by Alexander “Greek” Thomson, should not be seen in rivalry to Edinburgh, but as two hands of the same being, performing different roles at times, perhaps, but ultimately pulling together.

There is a real and present risk that in the drive to make Edinburgh a ‘world city' in the commercial sense, we make it more and more like just any other city in the world and, in so doing, diminish its status as a beacon of excellence in architecture and urbanism, and indeed enlightenment. In A Vision of Britain, I also suggested that the impact of new buildings could be softened by an acceptance of the existing street rhythms and plot sizes and that the buildings in a city such as Edinburgh are the individual brush strokes of a grand composition, which works because all the participants understood the basic rules and traditions, with harmony being the pleasing result. This lesson, is, I believe, still as relevant today as it was in the Scottish Enlightenment!

If I may make an impassioned plea, it is that we take most special care that the dynamic processes of growth that continue to shape this great city do not lead us to undermine that harmony. Should we not be concerned in this, as in all our cities, that our heritage is respected and new development woven into it in a way that creates a legacy for future generations? Just at the point where traditional urbanism is being recognized as having direct relevance to sustainability and therefore meeting the challenges posed by the environmental crisis facing us all, should we not be studying evermore carefully the lessons our successful cities have to teach us?

Happily, I feel a new consensus beginning to emerge in Scotland – a new kind of modernity, if you will. It implies that we can find effective ways of dealing with the big problems of our day, which do not oblige us to bury beneath our abstractions or our balance sheets the very things that actually make life worth living.

And it requires we build again the types of places we all know strike a chord in our, by now, rather bewildered hearts, however “modern” we are – places that convey an everlasting human story of meaning and belonging; built for the long term with greater attention to detail and to an innovative combination of time-tested techniques and the latest environmental technology which can produce, what will in time become the much more highly valued and ultimately sustainable heritage of the future.