A handful of high-profile examples perpetuated this belief. Undoubtedly, the creative reputation of Abbott Mead Vickers BBDO was built on David Abbott's elegant writing. And some of the most stunning ad work ever resulted from John Hegarty's art direction while in charge of Bartle Bogle Hegarty's creative department.
Thus was born the notion that the work was invariably skewed according to whether the creative director's background was in writing or art direction.
The reality is more complicated. For example, how come Collett Dickenson Pearce produced the Benson & Hedges "gold" campaign - one of the most visually memorable of all time - when John Salmon, a writer, was in creative command?
And Abbott himself suggests that a major factor in establishing AMV's fame for fine copy had a lot to do with the fledgling agency having many small clients whose budgets confined them to print media.
Hegarty makes no apologies for imposing his style on BBH - "if a creative director isn't doing that then what is he there for?" - and regrets it happens less frequently now. "Having some prejudice is a good thing," he says.
Today, it is even harder to make blanket distinctions between agencies with a predominantly "art directed" output and those where the emphasis is on word power.
Indeed, most shops make an effort not to be pigeonholed. Leon Jaume, the WCRS creative chief and a writer by training, contrasts his agency's stylish work for BMW and its quirky campaigns for 118 118 as evidence that it has won the fight against being typecast. "I love seeing stuff I would never be able to do," he says.
The TV scripts arriving at production companies bear out this change.
"In the past, you could often tell if the creative director was a writer or an art director," Laura Gregory, the Great Guns founder, says. "With so much crossover now it's rarely possible."
That said, creative influences linger. Some detect the fingerprints of Robert Saville, Mother's writer creative partner, in the agency's funny and populist work. "Robert is a writer who is also very visual," Damon Collins, the Mother creative director, says. "But he also thinks about strategy and ideas." Others see a direct link between VCCP's distinctive O2 output and the agency's art director creative chief, Rooney Carruthers. "Our three creative heads are all art directors and, although a lot of our output is copy-led, I wouldn't call it our signature work," Charles Vallance, the VCCP founding partner, says.
Rory Sutherland, the executive creative director of OgilvyOne and a writer by training, echoes this. "I would be dishonest if I denied that the history and background of a creative director doesn't have an influence," he says.
"And that's no bad thing if it drives work that's distinctive and original."
For the most part, though, the consensus is that agencies' creativity is not the product of their creative director's upbringing. "You can still see occasional signs, but it's patchy," Greg Delaney, the Delaney Lund Knox Warren & Partners chairman, remarks.
That is not to say more creative directors would not like their pet discipline to be reflected more in the output. "It's not fashionable to admit such a thing," Peter Souter, AMV's deputy chairman and former executive creative director, says. "But creative directors tend to be powerful personalities." Jaume agrees. "I bet that subconsciously we all try to do it," he acknowledges.
"We want to bring a part of ourselves to our work," Steve Henry, TBWA\London's newly appointed executive creative director, points out. "It's only natural."
So why do creative directors no longer exert their influence in the way many would like to? The answer lies with the changing demands of clients.
"Our clients no longer want us to be ad-centric but ideas-centric," Bruce Haines, the Leo Burnett group chief executive, argues. "There was a time when you could see the influence of Abbott and Hegarty in so many aspects of their agency's work. But that's an outdated concept now."
Moray MacLennan, his counterpart at M&C Saatchi, suggests it is because the industry as a whole is more talented and better trained. "Twenty years ago we were at a formative stage and feeling our way," he explains. "We were much more reliant on the gurus."
Other factors have also fuelled the progression, not least the breaking down of the boundaries between writers and art directors. It is a trend that begs a couple of important questions.
One is whether the emergence of creative teams claiming to be jacks-of-all-trades are a response to the changing media landscape or - as a lot of senior creatives fear - the result of colleges teaching their students that bright ideas are more important than craft skills. "Poorly executed art direction or badly written copy will ruin any campaign even if every other element is spot-on," Steve Stretton, the Archibald Ingall Stretton creative partner, warns.
The other is whether less rigid team structures will result in more art directors at creative director level (the majority of creative chiefs are writers). In general, writers' ability to articulate ideas and their greater willingness to take an interest in strategy has better equipped them for the top role.
Nevertheless, Liz Harold, one of the UK's leading creative headhunters, says: "I'm never briefed to find a creative director from a writing background. These days, agencies are much more concerned about finding a leader who can encourage their teams."
Many believe that more important factors define an agency's creative character than the route by which its creative director arrived in the job. One is how well the creative leader performs as advocate for the agency's work. "The creative director has become the sales director," Souter observes. "Selling the work is his most important job now."
Also important is how well they understand the new media channels. "The disposition of a creative director is still key," Andrew McGuinness, the Beattie McGuinness Bungay chief executive, affirms. "If he is a technophobe it can have a serious impact on the output."
Some things, however, don't change. "Agencies reflect the vision of their creative directors," Dave Alberts, Grey London's creative boss and a writer by training, claims. "That's our role and it always will be." But, whatever their background, creative directors must be able to spot a breakthrough communications idea versatile enough to be used across a range of media. "No creative director should allow his background to obstruct the route to the right solution," Paul Briginshaw, the Miles Calcraft Briginshaw Duffy creative partner, insists.
MacLennan has worked with writer creative chiefs including Jeremy Sinclair, Simon Dicketts and James Lowther, as well as art director leaders such as Paul Arden and Graham Fink. He says: "You'll always find differences in tone and style but all have the ability to spot the idea and work with it."
Nik Studzinski, who rose through the art directing ranks, recognises the importance of setting prejudice aside when approving work. "I like words as well as pictures," the Publicis executive creative director says.
A number of leading agencies prefer to sustain a balanced output through joint creative leaderships that embrace both disciplines. At Fallon, the creative department has been run by the writer Andy McLeod and the art director Richard Flintham for the past eight years. "It's not something we set out to do," Robert Senior, Fallon's managing partner, says. "But it seems to give us strategically robust ideas rather than 'fireworks' that look beautiful but are instantly forgettable."
Across the industry, the proportion of art director creative heads is on the rise, perhaps as a result of the idea that the fragmented media landscape calls for an emphasis on visual communication to cut through the clutter.
Steve Harrison, the writing creative director and managing partner of Harrison Troughton Wunderman, suggests that even direct marketing (the natural home of long copy) is increasingly image-conscious. "It's got to a stage where the competent writer is reticent about wielding his power for fear of being labelled old-fashioned," he says.
Others suggest that the internet, talk radio and even rap music prove there is plenty of life left in the written word.
Vallance does not dispute that, but predicts that art direction will grow in importance. "We may be the most literate generation that's ever lived but we're also the most visual," he declares. "This is the biggest cultural shift since the Renaissance."
WRITERS & THEIR CAMPAIGNS
Dave Alberts - Grey
Trevor Beattie - BMB
Nick Bell - JWT
Jeremy Craigen - DDB
Greg Delaney - DLKW
Tim Delaney - Leagas Delaney
Steve Harrison - HTW
Steve Henry - United
Leon Jaume - WCRS
Andy McLeod - Fallon
Gerry Moira - Euro RSCG
John O'Keeffe - BBH
Ben Priest - RKCR/Y&R
Robert Saville - Mother
Peter Souter - AMV
Rory Sutherland - OgilvyOne
Jim Thornton - Leo Burnett
ART DIRECTORS & THEIR CAMPAIGNS
Steve Aldridge - PAA
Paul Brazier - AMV
Rooney Carruthers - VCCP
Graham Fink - M&C Saatchi
Richard Flintham - Fallon
John Hegarty - BBH
Charles Inge - CHI
Ed Morris - Lowe
Mark Roalfe - RKCR/Y&R
Kate Stanners - Saatchis
Steve Stretton - AIS
Nik Studzinski - Publicis