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As things change, you notice how much else stays the same. In the 40 years since The Builder became ºÚ¶´ÉçÇø, the landscape of our towns and cities has evolved significantly, with new buildings and engineered structures seemingly everywhere. Yet it is remarkable how films and photographs of our home towns from the mid-1960s still have a very familiar air.

In fact, half of today's built environment is still pretty much exactly as it was. The buildings and infrastructure of 2006, especially in terms of housing, retail and transport, are certainly not as advanced as we anticipated they would be. In 1966, my parents had been living in their new house for almost a decade, a similar period of time that I have lived in mine. Built 40 years apart, their spatial dimensions and room planning are strikingly similar. The roads outside our two houses - also commissioned at either end of these 40 years - could be identical twins.

In 1966, the industry had its own exclusive department of state - the Ministry of Public ºÚ¶´ÉçÇø and Works - which is a far cry from the fragmented representation of the built environment within today's government, where architecture, housing, construction and transport are all sponsored by separate departments.

Yet the government's view of the industry has changed not a jot. In 1966, the MPBW had been given special responsibility for improving the efficiency of the industry, a quest that has hardly changed gear since, and has more recently been pursued through Sir Michael Latham and Sir John Egan's reports, the Movement for Innovation, Constructing Excellence and the Strategic Forum. The names change every few years but the marathon to improve the industry's efficiency has not ceased throughout the period.

The industry is still fragmented but certainly less so than in 1966. Many names have gone: remember the National Federation of ºÚ¶´ÉçÇø Trades Employers (since renamed and now subsumed into the Construction Confederation), the National Council of ºÚ¶´ÉçÇø Materials Producers (now part of the Construction Products Association), or the Institute of Quantity Surveyors (long ago merged into the Royal Institution of Chartered Surveyors, or RICS)? While a list of the main trade associations in 1966 would be largely unrecognisable today, the leading professional bodies (the Royal Institute of British Architects, the Institution of Civil etc) remain, as ever, resolutely unbowed, residing in the same buildings and with the same titles that they had in 1966.

The most notable change in our environment today, as opposed to say 60 years ago, took root in the 1960s and that was the move towards higher living. Until 1967, the government was encouraging high-rise blocks to get taller and half of all new housing was being provided in flats. The comparatively high standard for public housing was derived from the Parker Morris report, Homes for Today and Tomorrow, published in 1961. However, it was the Ronan Point collapse in 1968, accentuated by the removal of government subsidy a year earlier, that spelt the beginning of the end for high-rise fervour, seriously disabling the movement for industrialised buildings.

The love of high-rise blocks may have vanished, but another 1960s favourite, off-site prefabrication, is still with us. "Industrialised building" or "system building", as it was then known, was the "in thing" of the mid-1960s, having been progressively pushed since the war, although this is less a case of something remaining the same, more an example of ideas moving in cycles. Today's demand for more buildings to be manufactured off site is clearly an idea 40 years behind its time.

The architectural icons of the mid-1960s remain, of course, and were mostly in London: the Barbican, completed in 1969, introduced the concept of a living, working and playing environment all in the one complex; the Queen Elizabeth Hall and Purcell Room, completed in 1967, and the long-running saga of Lasdun's National Theatre - not completed until 1976 - on the South Bank have become monuments to their time, loved by many and reviled by most. Other major developments included the second stage of Gatwick Airport, finished in 1965, and several new "greenfield" universities.

The five iconic structures of the latest age also belong to London: Canary Wharf, the transformation of a disused industrial space into the vibrant Tate Modern; the landscape-altering Millennium Eye and the functionally-challenged but brilliantly designed Dome of the same name; and, last but not least, the Swiss Re building.

Yet, this fixation on the capital is changing, too. In the past decade, political devolution to the nations and regions has been matched by the significant regeneration of many towns and cities with Bristol, Birmingham, Manchester and Newcastle/Gateshead now transformed into inspirational places to live and work.

The biggest change in the processes of creating the built environment over the past 20 years was surprisingly pre-empted by the Prince of Wales - one of several absentees from the Hall of Fame that I'm sure will raise some eyebrows - in a no-nonsense speech to celebrate the RIBA's 150th anniversary in 1984. The speech is best remembered for just two words - "monstrous carbuncle" coming to be carved on the headstone of modernist architecture. Yet, community architecture, pastiche housing, a charge towards "less is more" in building and a gradual move to recognising that the client should lead - a baton picked up with such force by Sir Michael Latham 10 years later - have all taken strength from that royal intervention.

It was surprisingly easy to choose the 40 people who have, more than any others over the past 40 years, changed what needed changing. Agreeing that they are the right names will spark a debate that will probably never end.