The time of day and Dame Thora's delightful performance are not unrelated. One Foot in the Past has proved to be a successful way of translating stories architectural to a reasonably large television audience. So much so that the Beeb has taken the risk of lifting the show into a prime-time slot. Basil Comely, the series producer, "hopes for an audience of up to four or even five [by which he means, in Beeb-speak, four or five million], although we'd be happy with two or three". Given that there are two million members of the National Trust, many of whom might come in from the trimming the yew on summer evenings to settle in front of the box for a quick telly supper, before tackling the greenfly menace, One Foot in the Past stands a chance of netting the big audience Michael Jackson, controller of BBC2, thinks it just might.
Big television audiences, however, are not drawn to subject matter alone, no matter how inherently rewarding. Stars are usually needed to boost the viewership, and this is where Dame Thora steps in. In "Thora Hird goes Modernist at the Midland", this most professional of Lancashire lasses takes viewers on a tour of the remarkable Midland Hotel on Morecambe Bay designed in a "Jazz Moderne" style by the talented and eclectic architect Oliver Hill for the London, Midland & Scottish Railway and opened for cocktails, waltzes, sun, sea and fun in 1933.
Dame Thora, who grew up in Morecambe, remembers the opening well, although invitations for the grand event were strictly reserved for what she calls the "fast set" from Manchester and Bradford. Tucking into a dish of deep- fried Morecambe Bay prawns in the hotel's swish, streamlined restaurant, Dame Thora recalls the shock - a delightful one, as it turned out - when this gleaming white concrete and steel "monster" rose, as if from the bracing waves of the Irish Sea.
The Midland, with its posh food, smart dances, its murals by Eric Ravilious and relief by Eric Gill (who wanted something much saucier than the executed design that, sadly, has long since vanished from this grand Modern hotel), made Morecambe positively glamorous; for a few years anyway.
Not only is Dame Thora a wonder to watch, but she is also fluent in her architectural description of the building. Fluent too as she glides across the hotel's ballroom floor with her old Morecambe dancing partner, Freddie (whom she refers to as "Frayd", which is a nice little joke for Meet the Wife fans). Dame Thora first danced with Freddie, we learn, 70 years ago.
The clever thing about this neat bit of casting is that Dame Thora does not try to steal attention from the building; instead, she uses her talent to make it come to life, which is a very different talent from those who want to be bigger, noisier stars than the architecture they are paid to investigate.
Last week, in the first programme of the new series, One Foot in the Past had Jack Charlton, the retired manager of the Irish national football team, trailing gently and sentimentally in the wake of childhood jaunts along the River Coquet, Northumberland. In the next few programmes, it promises Ralph Fiennes, who "retraces the steps of his hero, Lawrence of Arabia", at Clouds Hill, Dorset, and Rupert Graves on the fascinating Birnbeck Pier, Weston-Super-Mare, on which he played as a schoolboy before growing up to play schoolboys.
Intermixed with these "prime time" stars are heritage experts including Dan Cruickshank, Gavin Stamp and Simon Thurley.
The move towards "stars" is a sensible one given that maximum ratings are, or so it seems, the all- important factor in making a contemporary television series. There is, of course, a danger of trivialising a subject like architecture. Most of the best presenters in the past have written their own scripts, but to a formula they know should work well with a given audience. Betjeman, for example, played increasingly on whimsy as he grew older, knowing that to express the full range of his extremely knowledgeable opinions on the subject could alienate him from the vast, National Trust house-visiting audience that also bought his poetry and recordings of his poetry in prodigious and profitable quantities. He was careful to play safe with suburbia, for example, which he didn't actually like, but thought terribly English and very funny. He was sweet and sentimental when, really, his wit was razor sharp and, when he wanted it to be, cutting, snobbish and even cruel. An actor at heart, he played the role of old Betj, the nation's favourite teddy bear, to perfection.
Sir Kenneth Clark, by way of contrast, was the last of the presenter mandarins, a chap from some distant and imperial past garbed in immaculate and ever-changing silk tailored suits. He appeared so confident and important that surely he knew everything that anyone could ever possibly wish to know about the Italian quattrocento. In fact some of the lines in the script of Civilisation are cavalier, while others are sweeping to the point of being banal. That wasn't the point: at the time, Civilisation brought a sweep of well-polished cultural history to the feet of those who were not so well provided as we are 20 years on with sophisticated guidebooks and access to cheap travel to Florence and Siena.
It is unlikely that Lord Clark would be asked to make prime-time TV today, unless, perhaps he could have made the sort of populist connection Luciano Pavarotti did when the great tenor sang "Nessun dorma" to football crowds during the Italia 90 World Cup. Here was the solo star of the auditorium brought into touch with the heaving chorus of the stadium.
The popular touch is what seems to matter most today. So, the BBC Design Awards programmes broadcast on Wednesday 5, 12 and 19 June have Janet Street-Porter, mistress of the I'm-not-really-middle-class accent, guiding us through what teams of judges chosen by the BBC believe to be the best new developments in the fields of architecture, product design and graphics. The upbeat, in-your-face Street-Porter style has been judged the right one to connect with an audience that is being asked to vote on what they think are the very best new designs in these categories. Street-Porter did, in fact, study architecture in her yoof, and worked for a while as a journalist specialising in design; she also lives in a house in fashionable Smithfield (and has done so for some years) designed by her old friend Piers Gough, a colourful architect with a decidely popular touch (Gough designed the swish and amusing public lavatories in Notting Hill Gate that have since become a landmark for London cabbies). Street-Porter has the credentials, but the key thing is that she is seen to be taking the elitist element out of discussions on design and architecture.
Piers Gough, by the way, together with Sir Norman Foster, Sir Richard Rogers, Richard MacCormac, Phillipe Starck and Nicky Haslam all appear in BBC2's Public Property (every Tuesday), an inspired look at how leading architects, designers and decorators can tranform tiny public projects from sows' ears to silk purses. In this series, the architects are not asked to be presenters as such, but to walk and talk through the filming as if the camera, the failed batteries, the hair-in-the-gate and so on, did not exist.
A technique that deflates egos, it is a modest one and works well. This is largely because we, the viewer, are genuinely interested to see what a big-name designer makes of the kind of commission normally given to the office junior or else to an architectural practice that considers a kitchen extension to a bungalow in Bromley its Pompidou Centre or Waterloo International.
A fourth new BBC2 series on architecture, Building Sights (Mondays, 8.50pm), a kind of Desert Island Buildings, begins another welcome run this spring, bringing a blend of stars and lesser-known characters and experts to the small screen. This series includes Germaine Greer (Glyndebourne Opera House) and Damien Hirst (Worsely Building) along with architects Will Alsop (Hauer/ King house, London), Richard Rogers (Alton Estate, Roehampton) and Zaha Hadid (Willis Corroon, Ipswich), Posy Simmonds, the cartoonist (Wood Street police station, City of London), and the poet Simon Armitage (Humber Bridge).
All this adds up to a fair amount of coverage for architecture and design this spring and summer, especially when there are documentaries on William Morris and Charles Rennie Mackintosh in the pipeline. It remains, however, a difficult subject to tame for tiny, flickering screens. At best, an interesting presenter and a well-informed script can help, along, of course, with the best camerawork and editing skills available, to stimulate enthusiasm in buildings ancient and modern. At worst, "stars" tend to dominate the proceedings, blotting even the grandest building from view with grotesque manners or inflated vowels and manners.
An ideal film on architecture might have the camera moving very slowly as in scenes from Alain Resnais's Last Year in Marienbad (1961) or Andrei Tarkovksy's Nostalgia (1984); but, who, in the age of instant boredom, nano-second attention spans and addictive channel-hopping could watch images as slowly changing, yet as intelligently revealing as these (save, perhaps, for Victor Lewis-Smith, the sparky TV critic who claims to be entranced by the BBC2 colour test card)?
In fact, what the BBC is doing is more or less the right way forward, a balance of stars and experts, gor'blimey and golly-gosh presentation, polished nostalgia with Dame Thora and intelligent thought from professional architects not being asked to be stars but doing instead what they do best - designing.
Of course, there are other ways of filming architecture on television from drama (expensive) to other forms of documentary that rely more on buildings than talking heads. In the meantime, one hopes the BBC will keep up the renewed interest it has shown this spring. But, while other projects are being fettled, my own selfish plea is that Dame Thora be wheeled out again to take us on the gentlest of whirls through the forgotten treasures of the north of England, and, should she need a bit of help with the script, that other architecture buff, Alan Bennett, should be chivvied from his Hampstead lair to help. In the meantime, I am off to watch "Thora Hird Goes Modernist at the Midland" on the office video for the third time.