As a cub reporter I once went to interview Colonel Richard Seifert, then famous, or notorious, as the architect of Centre Point - at the time the tallest building in London, soon to be overtaken by the NatWest Tower, which Seifert also built. How, I wondered, could one architect, whose work was synonymous with high-rise concrete monstrosities, have been commissioned to erect more London buildings than Christopher Wren ever contemplated?

“I understand the planning regulations,” said the colonel, fixing me with a disconcerting smile. “I deliver on time, I understand my clients, and I give them exactly what they want.” That was not the whole story. He had a very clear idea of what he himself wanted and, ideally, he would have liked to rebuild all London in his image. He told me of his vision of great battlements of tower blocks, surrounding, and dwarfing, the very few old sites that he thought worth conserving. Luckily, he was defeated in the end by the very bureaucracy he thought he had mastered. He still managed, nevertheless, to complete more than 500 office blocks in Britain and Europe.

For anyone who wonders whether any of today's architects could influence a city to the same extent, a trip to Edinburgh in this festival season would be instructive. In this place of architectural marvels, there is a new name to conjure with. The successor to Adam, Playfair, Hamilton, Bryce and Gilbert Scott - the creators of Edinburgh's celebrated skyline - is Allan Murray. His may not be a name to conjure with in the wider architectural world, but in terms of current projects and masterplans in this city, he dwarfs everything that his more famous predecessors constructed.

It is hard to take a walk from the narrow wynds of the 17th-century Old Town to the stern splendour of the 18th-century New Town without stumbling across a Murray site, either completed, in construction or in contemplation.

Walk down the Royal Mile, past a new Allan Murray hotel, from where you may observe the site of an Allan Murray redevelopment in the heart of the Old Town, proceed down the Canongate, where a couple of fine old buildings are to be demolished to open up a new Allan Murray shopping precinct, then head towards Leith Walk, where the glass-fronted Allan Murray office complex successfully conceals the once scenic Calton Hill. Then observe the sprawling and hideous St James Centre to your left, which is, mercifully, to be razed, to make way for... another Allan Murray complex.

Or instead just click on to Mr Murray's impressive website where all these and more are collected together under brave new titles such as Caltongate, Soco, St James Quarter and Edinburgh Park. That so many precious sites have been assigned to just one architect, without any noticeable public reaction, is a remarkable commentary on the way in which British cities are allowed to develop with no apparent control over how or even why they are doing so, along with a minimum of public accountability. In any other European city - Barcelona, say, or Rome - there would be high-profile competitions and rigorous scrutiny of any large architectural project. Here, the developer, and the architect of his choice, is king.

I like one or two of Mr Murray's smaller buildings, but his masterplans and big developments strike me as bland and undistinguished. One commmentator has described his office buildings as “wallpaper architecture”. His practice was set up barely 15 years ago, but his success is in stark contrast to that of other Scottish-based architects, some of whom have been nominated for the Stirling Prize and won awards in England and abroad, but have never been given contracts on anything like the scale achieved by Mr Murray.

The truth is that when it comes to developing our cities, design tends to take second place to the more prosaic imperatives of the market. The developer who can bring in a project under budget, on time and without offending planning restrictions has a head start on his rivals, however imaginative their approach may be. The architect who can be relied on to deliver those objectives will be favoured over his starrier competitors. The planning committee giving the go-ahead simply wants to know that the scheme is trouble-free. The outcome may be mediocre, but it is safe and reliable mediocrity rather than dangerous originality.

What is happening in Edinburgh may be more striking in a city renowned for its great architectural heritage than elsewhere - but the outcome is reflected in most of our major towns and cities. It is nearly ten years since the architect Lord Rogers of Riverside published his ground-breaking report on urban renaissance, in which he said that design must always take primacy over planning laws and expansion plans. He also said that the public should be more involved in developments that affect the look of the places they live in.

Neither of those aims have yet been realised, and Edinburgh's example suggests they are still a long way off.

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