Collett Dickenson Pearce was both adland's Camelot and its Brigadoon. Like them, the agency's almost mythical status belies the relatively short time in which its star shone brightest.
Indeed, it's almost impossible to believe that a marcoms landscape that has changed beyond recognition since CDP opened for business 50 years ago this month could ever have accommodated so anarchic an organisation.
No agency was a product of its time in quite the same way as CDP. Its arrival coincided perfectly with commercial TV's high summer. And it mastered the medium brilliantly and memorably. Who needs reminding that "Happiness is a cigar called Hamlet" or that "Heineken refreshes the parts other beers cannot reach"?
No agency had a more profound influence on the course of UK advertising or became a more fertile breeding ground for creative talent.
What's more - and as the 500 former staff gathered in London this Thursday to celebrate the anniversary of its founding will testify - no other agency has generated such long-lasting affection.
Much of that love and loyalty was directly linked to CDP's culture and business principles whose relevance within today's rapidly evolving industry is probably a more open question.
After all, wasn't CDP born in an age when clients with limited knowledge of advertising and not obsessed by research were willing to stand back and let agencies weave their magic? Wasn't it easier at a time when the ad business was thriving and 15 per cent commission was the norm to tell a client that if he didn't like the creative work, he could go forth and multiply?
And wasn't its swashbuckling approach helped by having no external shareholders to satisfy and no parent company demanding that it hit the numbers?
Finally, didn't CDP become so dazzled by its mastery of TV that it was blinded to the way technology was changing the way advertising was produced and faded away just as surely as Brigadoon did into the Scottish mists?
The answer to all these questions is yes. Yet there are still many who believe that today's industry still has much to learn from the way CDP thought and acted during its Camelot years.
CDP espoused values that still hold good despite a media world now much more sophisticated and fragmented. Creativity was at the heart of everything it did - and it was prepared to pull in the best people it could find to keep its product fresh.
It eschewed blandness and over-complex messages. Its ads were witty, confident and relevant and never self-indulgent, and they developed relationships with consumers long before the digital revolution.
Its campaigns were consistent and long-running in a way rarely seen today because they were always linked by a strong central idea. And if those campaigns won awards - which they did by the sackload - that was merely the by-product of what was, first and foremost, effective advertising to enhance a client's business.
How did CDP manage this? A lot of ex-staffers believe its fostering of an esprit de corps through having fun - a rare commodity in adland these days - had a lot to do with it. "It was like being an undergrad again," one recalls. "We never wanted to go home."
The result was an output of astonishing durability. What work created today would be recognised by consumers more than three decades later as many of CDP's ads were when they reappeared across London in the run-up to the reunion?
Sony "balls" and the Cadbury "gorilla", perhaps. But as one agency chief asks: "How much work do we do now that we're proud of and that people remember?"
To view CDP's iconic work, visit campaignlive.co.uk
ROBIN WIGHT - Founder, WCRS; CDP copywriter, 1968-1970
"The big thing we can learn from CDP is the importance of being a 'conviction brand'. The agency had an inner belief about how things should be and didn't cowtow to the false gods of market research.
"It wasn't that it didn't do research.
It just used it in an illuminating rather than in a judgmental way. I once helped create a print ad for one of Ford's models, which was based on the fact that its long bonnet protected people better in accidents. The ad was all set to run when John Pearce ordered it to be pulled because if featured the image of a crashed Ford. CDP always did what it thought was right for the brand, not for the agency.
"There are a number of successful agencies, such as Bartle Bogle Hegarty, that remain 'conviction brands'. But there are too many others that have turned into highly skilled chameleons. CDP was never like that.
"CDP did well-branded ads that people liked. But it wasn't a 'creative fest' and never believed you had to start every new campaign with a blank sheet of paper. Today, there's too much zig-zagging."
SIR FRANK LOWE - Founder, Lowe Howard-Spink; CDP account executive, later managing director, 1969-1981
"I do find it interesting that so many people seem now to be recognising what CDP was to British advertising. However, the idea that it could be recreated is, in my view, nonsense.
"The whole industry has moved on in so many different ways that, while the philosophy of CDP still pertains, the work was of its time. The agency had people and clients and a system that worked then but which probably wouldn't work now.
"What's required is a new generation, one that's post-Thatcher, post-Generation X, possibly even post-Generation Y, that will create a revolution in advertising communication through all the media that are now out there (advertising in classical media, internet/CRM, sports marketing, PR etc) and which will once again put the quality of the work ahead of the profits.
"If people do that, as we did at CDP, they may be surprised to find that they will make quite a lot of money as a by-product of creativity, not as a reason for creativity.
After all, this is what happened historically in most forms of art from the Renaissance to rock and roll."
JULIAN HOUGH - Founding partner, Engine; CDP account executive, 1984-1991
"Some of today's agencies are focused on creative honours. That didn't happen at CDP. Doing a one-off ad for a charity to win an award would have been unthinkable. The agency created advertising for big brands that was intended to boost a client's business. It won lots of awards - but it never set out with the intention of doing so.
"CDP was a place which believed in itself and where people believed in each other in a way that would be the envy of most agencies. As a very young account man, I remember a client being very rude to me in front of other people. When Nigel Clark, the joint managing director, got to hear, he rang the client, bawled him out, demanded he apologise to me and warned him such behaviour wouldn't be tolerated. It's hard to imagine that happening today.
"At CDP, people bonded through having fun and that's why staff were so loyal. Sadly, the time to have fun isn't available to people any more."
STEVEN HESS - Managing partner, Weapon7; CDP planner, 1989-1994
"CDP's business was totally focused on fantastic creativity. Today, too many agencies think they're selling time so that there's less emphasis on ideas.
"Also, in John Salmon, then CDP's chairman, it had a true gentleman who treated his staff with consideration and respect and made them want to do their best work. I don't believe enough people in the industry are treated like that today.
"CDP shaped my professional life because it fundamentally believed in its product. I doubt that many of today's top ten agencies are run jointly by the chief executive and the executive creative director. That's what used to happen at CDP and I think that's very important.
"The great thing about the agency was that it was a melting pot of people from a diverse range of backgrounds and it wasn't afraid to take on provocative people. Agencies are now much more conservative about who they hire and where they hire them from and that's leading to blandness."
JOHNNY HORNBY - Founding partner, CHI & Partners; CDP account director, 1994-1998
"At a time when the industry is so badly bruised, we should remember how much pride CDP had in what it did. It's about time we started to feel more proud of ourselves again and a lot less humble. We need to get our star status back.
"CDP did brilliant work that made brands famous. I think agencies have forgotten what they're about. Of course, marketing has got a lot more complicated and consumer behaviour has moved beyond a time when it could be affected by a few brilliant ads. Yet our ability to be so creative that we can change the course of a business has never been more important.
"There are too few agencies today that follow CDP's example of refusing to roll over at a client's behest. Some of the best agencies still have the chutzpah to act if they think a client isn't keeping his part of the bargain. But there aren't enough that are prepared to do it.
"CDP did it because of the confidence that grew out of being bloody good at what it did. I think there's an opportunity for a new CDP-inspired advertising age."
LORD PUTTNAM - Labour peer; deputy chairman, Profero; CDP group account head, 1962-1967
"CDP teaches us that agencies that don't spot and hire the best young talent available condemn themselves to death. Every Wednesday afternoon, a line of job-hunting creatives would sit outside Colin Millward's office waiting for him to look at their work. That's where I first saw a couple of twentysomethings called Charles Saatchi and Alan Parker.
"Today everybody frets so much about the bottom line that creativity isn't what it was. CDP was so confident its creative work was right that, as an account man, I was more scared about returning to the agency having failed to sell an ad than anything a client might throw at me. In CDP's time, press ads were often better than the editorial. It's not like that any more.
"I think it's possible agencies today are reluctant to hire people that are hard to handle. I was a pain in the arse, but Millward defended me and CDP was able to accommodate me.
"CDP made us proud of what we were doing. John Pearce fired Ford not just because it was interfering with the ads but because of the effect this was having on those who were creating them."
HUGH BURKITT - Chief executive, Marketing Society; CDP account supervisor, 1972-1974
"The big lesson that CDP can teach today's industry is that brands must be confident, charming and have an air of authority about them if they're to be successful.
"The great thing about CDP's work was its consistency. Its campaigns always had a strong central idea even if - as with Hamlet cigars - they took a while to gel. That's just as important today.
What's more, the agency knew that for TV commercials to really engage, they must be well written. Too much of today's TV work relies on visual trickery.
"I also think that today's creatives have got too close to clients. That didn't happen at CDP. The result was a freshness about the advertising that reflected the outside point-of-view, which is what clients should be paying agencies for.
"Of course, CDP also taught what can happen when self-confidence becomes a supreme arrogance and being so sure you know what's best that you fail to adapt to a changing market."
DAVID ABRAHAM - Chief executive designate, Channel 4; CDP account executive, 1986-1990
"CDP proved that if you wanted to produce creative work of the highest standard, then compromise is the enemy. Of course, the fragmentation of media - and the emergence of media from the backroom - has changed the ad business enormously since CDP was in its prime. But what's been lost as a result is the pre-eminence of the creative agency.
"CDP showed what could be achieved by smart and thoughtful people working with the best directors and how it was possible to spawn talent that's been successful right across the creative industries.
"It's worth remembering that CDP was special because it accommodated so many different characters. They were often awkward and truculent, which made the agency a tough place in which to work, but they didn't suffer fools. And if you want brilliant creative ideas you need people like that around you.
"I think another important factor in CDP's success was the number of older and more experienced people on its staff. Wisdom was valued. I think the industry has lost too many of its grey hairs."
MARK WHELAN - Creative director and founder, Cake; CDP account manager, 1992-1994
"The thing that most struck me about CDP was the incredible camaraderie, how decent all its people were and how well they looked after each other. The evenings in the seventh-floor bar and the seven-a-side rugby team all exemplified that.
"The result was that, having been encouraged to strike out on my own and set up Cake, I resolved to instil the same kind of culture. I don't believe in climbing all over people to get to the top.
"In its heyday, CDP was Mad Men personified. But that's because agencies then weren't subject to the same degree of accountability. Advertising today has become much more scientific. CDP's decline marked the end of a golden era and the industry is, perhaps, the poorer for having lost some of its spirit."
GRAHAM FINK - Executive creative director, M&C Saatchi; CDP art director, 1981-1987
"CDP reminds us of the importance of 'brutal simplicity'. It was one of the first agencies whose ads talked about one thing rather than many things. That's just as important today.
"What CDP did then - and, I suspect, few agencies do now - is to have new creative work pinned to the walls where everybody could pass comment on it and suggest how it could be made better.
"I think a lot of agencies today fight shy of employing brilliant, but unpredictable, creatives like Dave Horry and Alan Waldie. There are a lot fewer characters around and a lot more fear. And the industry is the poorer for it.
"Small wonder, perhaps, that there's so few of the long-running campaigns around now like the ones CDP created for Fiat, Heineken, Hamlet and Olympus cameras. Who is doing work today that will still be talked about in 30 years' time?"
MARK LUND - Chief executive, COI; CDP group account head, 1983-1990
"CDP produced advertising that people weren't just attracted to but enjoyed and that's a very modern idea. The agency's philosophy was to create work that people would be struck by and engage with. That's more important than whether or not an ad is a good strategic fit.
"The other lesson from CDP that still resonates is the importance of getting the best people you possibly can to bring creative ideas to life. It doesn't matter how great the script is if the film isn't very good.
"CDP once sent me to Edinburgh three times to sell the same poster to Scottish & Newcastle Breweries because the agency wouldn't change it. I'm not suggesting that should happen now but it shows how much CDP believed that the most important client was the consumer.
"I don't know if today's agencies are too eager to make a compromise with clients. But I do know that there are clients who want the agency to disagree with them if it thinks it should."
CLASSIC CDP CAMPAIGNS
Advertising from a golden era... (clockwise from bottom left) the classic Collett Dickenson Pearce campaigns for Hovis, Heineken, Fiat, Cinzano, the Metropolitan Police and Hamlet are still remembered with fondness today by the average consumer