The story is likely apocryphal — and so disgraceful I almost hesitate to tell it — but it goes like this. On the night of 14 November 1940, as more than 500 Luftwaffe rained bombs on the people of Coventry, the newly appointed city architect Donald Gibson was watching the fires.

Gibson had been appointed to the newly created position of ‘city architect’ three years earlier by the radical Labour council that had come to power in a local election. His job was to modernise what was then Britain’s best-preserved medieval city, and build the ideals of social justice and equality into the city’s brick and mortar.

That night, as swathes of the old city fell, Gibson was supposedly hurrying back and forth between the window and his architectural models to see which parts of his plan he could now put into place, the last logistical obstacles having been blown to convenient smithereens.

I should stress again that this probably didn’t happen. But the story illustrates neatly — probably a little too neatly — the old accusation that 20th-century architects and urban planners cared about their own grand designs far, far more than they cared for the people meant to live in them.

Things are rarely so simple, as I discovered listening to How to Rebuild a City, another stellar edition of Radio 3’s Sunday Feature. This weekly documentary slot remains one of the most consistently interesting programmes being broadcast. Among its other merits, it makes a lovely change from Auntie 3’s dish-dull weekend broadcasting slate of beardy jazz, spoken word and Desert Island Discs rip-offs. This weekend I heard not one but two classical singers perform treacly, testicle-wrenching covers of the Beatles’ ‘Blackbird’. (Two, as the saying goes, begins to look like carelessness.)

When Coventry advertised for a city architect, they wanted a modernist; the job advert stipulated that no one over the age of 40 should apply. Donald Gibson was all that and more, a firebrand who was unafraid of talking tough to power. ‘If the front door didn’t get him what he wanted, he was quite prepared to go in through the back door,’ says one historian interviewed here, and I have no choice but to commend them for their startlingly unselfconscious choice of words.

Another rumour holds that King George VI wept when he saw the wreckage of Coventry Cathedral. When reconstruction began, Princess Elizabeth (later Queenie) laid the first stone. As she picked up the cement-smeared trowel, Gibson turned to her and said: ‘Slap it on thick.’

Coventry’s redesign is the most prominent and ambitious example of an architect working to remodel an entire city in modern Britain. As such, it excites a lot of strong opinion from different tribes. Much is made, more or less constantly, of the need for ‘balance’, a word that means different things to different people. To broadcasters, balance means the act of sitting people who hate each other in the same television studio; to politicians, it means ‘someone saying what I want them to say’. For my own part, I put my faith in detail — and How to Rebuild a City was detailed, thoughtful broadcasting.

Many of the city’s medieval buildings were demolished in the 1950s to make way for unremarkable housing, not modernist fantasias. In 1965, only 34 timber-framed buildings remained in the city — to redress the problem, the city started moving threatened buildings on to Spon Street, which became a sort of medieval Disneyland. Our host visits with an architectural historian, who gives the only possible verdict: ‘Really weird’.

Yet the rebuilt Coventry became as much a part of British history as the première of Benjamin Britten’s War Requiem at Basil Spence’s superb modernist cathedral, as much a human record as the ruined apse of the old church, which soars unsupported into the air like the roodscreen of some immense annihilated altar. Coventry’s monuments of post-war optimism, though, were later mocked by the collapse of the car industry in the 1970s and the area’s breakneck deindustrialisation. No doubt London’s South Bank would look equally sarcastic if the city had failed to thrive around it.

Today City Centre South is slated for a bland £300 million regeneration project, which is not half so mad as what sits there now. Much of the old plan will be lost. The original mastermind, Gibson, would have approved: he believed buildings should be torn down every 50 years and rebuilt in the modern style. I think we may well regret tearing down what we do. For now, if you want to see Coventry’s history, you should visit fast.