Peter York On Ads: Taste the nostalgia for 'The Sweeney' and sideburns in a sausage casserole

'Life on Mars' gave many mature TV viewers a funny moment. All its retro reconstructions were convincing at first glance. And as all the critics noticed, the important things seemed every bit as awful as they really were. The drab naff-ness of clothes and cars ('LoM' was set in Manchester, after all). The racism, sexism and minor corruption of some police characters. The poverty of just about everyone's aspirations (a key Eighties word).

But at the same time it worked you over. A 50-something friend told me he felt as if he'd had the knock-on-the-head – a favourite device of the films they showed on daytime TV in those days – and gone down the swirly-whirly hole to the Seventies.

The business of collecting demotic drek is miles better than it used to be. There are curious museums full of it, like the Marketing Museum in Notting Hill, stacked with those terrible, compelling sweet wrappers and grippingly hopeless giveaway toys. There's the Advertising Archive somewhere up in East Anglia, which has posters and double-page spreads and, crucially, most of the commercials from 1955 on.

Although they wiped some important early TV recordings, there's still a lot to watch. Art directors on 'Life on Mars' will have been spooling around with 'Sweeney' and 'Minder' tapes, whooping when they saw giant collars or bronze Cortinas, council flat carpets or first-generation black vinyl sofas.

The general idea that the Seventies was the Decade That Taste Forgot is a very dated Eighties one. (Read Michael Bracewell's brilliant new 'Roxyism' to see just how inventive and fastidious Seventies people could be.) There's something to learn, for instance, from how practically everyone in the UK managed on what seem like hopeless net incomes; how people who seemed rich then absolutely weren't by today's standards. And from what people did without American levels of "choice" – in television, travel and clothes. Did it make them more resourceful and content, or just resigned and irritable?

So when we see old TV ads with old production values, and the old narrative approach without computer tricks, where does it hit us? Not the top 20 work like Smash Martians, BA's 'Moving Cities' or Rossiter and Collins splashing Cinzano around – that's all art now; we're talking about the more generic stuff.

And what about things that really look like the old stuff, but aren't, like the new Colman's casserole ad. Sometimes I get a ghost in the machine – a vintage ad that's somehow slipped into my reel of the week's commercials. And I find myself wondering if it's pastiche because they're so clever now. You have to check when it showed and where.

But there's no question – this Colman's ad is real; it was on GMTV last week. But everything about it looks period. It's for a casserole mix – when did you last visit this sector? – and it's got a fast narrative, too. A glowing gas flame, a ker-ching as the knife comes off the magnetic rack, and a great deal of speedy slicing and dicing and onion tears.

Then into the casserole, orange Le Creuset, and on into the oven – a traditional gas stove, not a built-in or a stainless-steel cooker. Then it's out with a cheery oven glove and out on to the laminate (absolutely not granite, marble or Corian). As the action proceeds, it says Bish Bash Bosh, then Real Good Nosh!

Could they just think that a convincing Seventies style will add value to a casserole made with sausages and a packet of granules that look just like Gold Blend?