It is hard to imagine Margaret Thatcher, at any age, dancing herself giddy around the village maypole. Not when there was work to be done. But for all her Puritan upbringing and Cromwellian self-certainty, she was generally happiest in the company of cavaliers.

With a change of wardrobe and rock-god hair, Cecil Parkinson and Alan Clark could have fitted-in well at the Stuart court. Likewise, the two men who did most to define and refine Thatcher’s public persona, Gordon Reece and Tim Bell. In so far as the Iron Lady kept court, these two ‘image men’ were at the heart of it.

Last week surviving veterans of Thatcher’s Old Guard gathered at St Paul’s Church, Knightsbridge, for a thanksgiving service for Lord Bell’s life. There were also leading figures from the advertising and public relations worlds of which Bell had been such a buccaneering force of nature. But it was Bell’s political service that will be remembered by historians long after the controversies that shaped his professional career are distilled into tales of inspiration and warning for those in public relations.

In particular, Bell’s shrewd advice to the Conservatives over three victorious general elections campaigns (1979, 1983 and 1987) and his continuing loyalty to Thatcher long after her flame had flickered and dimmed were acknowledged at St Paul’s, Knightsbridge.

But there is one part of the myth that needs qualifying. It concerns the famous “Labour Isn’t Working” poster. In 1978 the advertising firm Saatchi & Saatchi won the Conservative party account and put Bell in charge of it. The poster was an early result. it is widely credited – even by Lord Thorneycroft who was Conservative party chairman at the time – as having won the Conservatives the 1979 election. Twenty years later, Campaign magazine voted it the “poster of the century.”

In fact, the “Labour Isn’t Working” poster that supposedly won the ’79 election and made Thatcherism possible was plastered across all of 20 billboards in the summer of 1978 in the belief that the Labour prime minister, James Callaghan, was poised to call an autumn general election. Created at short notice by Andy Rutherford and Martyn Walsh, the queue of the unemployed was, in reality, a cadre of Hendon Young Conservatives. Unfortunately, only twenty of them turned-up for the photo shoot, so the infinity-stretching queue had to be generated by getting them to dress-up in multiple outfits and postures, which were then replicated to give the impression of a multitude.

The poster was a small part of Saatchi & Saatchi’s campaign and, given its limited release, would have attracted scarcely any attention had not the Chancellor of the Exchequer, Denis Healey, complained in the House of Commons that the poster was a work of deception because it did not feature real unemployed people. The Tories were, in consequence, “selling politics as if it was soap powder.” This the media did report.

What is difficult to buy is the notion that the publicity for the poster generated such a surge in support for the Conservatives that Callaghan decided not to call an election in the autumn of 1978 and instead delayed until May the following year (by which time the Winter of Discontent had interfered with Labour’s re-election chances). In the summer of 1978 the Conservatives were leading in the polls. But in the two months directly following the poster’s launch, Labour regained the lead, a recovery that convinced Callaghan that he had time on his side. The best that can be said for the poster is that without it Labour might have enjoyed an even greater upsurge. But Callaghan’s decision to delay would have remained the same.

It is true that a variation of the poster re-appeared in a different format during the 1979 election campaign, with the slogan updated to “Labour Still Isn’t working.” But to attribute its return to the securing of Thatcher’s 43-seat majority is a theory without evidence to support it.  At the beginning of the election campaign, just before the poster went back up, the Conservatives were polling around 50 percent. From that high, they slid gently but continuously, ending on election day with 43 per cent.

So why, when Tim Bell and Saatchi & Saatchi really did achieve so much to improve the advocacy and persuasive powers of Thatcher and her party during the 1980s has the 1978 poster come to embody that success?

Perhaps because it heralded an era when Britain finally became good at selling, rather than making. It is therefore convenient to highlight it as illustrative of the moment when – to Healey’s horror – ad men really did move up in the world from soap powder to politics.

As well as exemplifying the muscle of the communications industry, it perhaps also suits those who loathed the Thatcher years to imagine that their long drawn-out nightmare was made possible by the glib skills of the ad men with a slogan that implied – oh, the bitter irony – that the Tories had a better solution to curb unemployment.

Both theories are over-stated. Good though they were at it, Tim Bell and Saatchi & Saatchi did not bring political advertising to Britain. The main parties had employed advertising firms as advisers throughout the twentieth century. “Labour Isn’t Working” involved a decent pun, unlike “Safety First” (1929) or “Life’s Better with the Conservatives” (1959) or, for Labour, “And Now – Win the Peace” (1945).

Actually, “For the Many, Not the Few” is a pretty memorable slogan. It succinctly conveys what the Labour pitch is all about. It also has historical resonance (Percy Bysshe Shelley’s “ye are many – they are few” and the re-worded Clause IV). And it would be toasted as a work of genius if it had resulted in Jeremy Corbyn as prime minister. Might that be why nobody is taking the credit for putting it up on the billboards and backdrops?