In those days I was a great admirer of Rowntree's advertising (the Kit Kat panda ad is perhaps the most famous). But the Rowntree crown was soon to be stolen by Marmite, who took the old "love it or hate it" adage about their product and ran with it in a way that makes Pheidippides look like a sprinter. Here's an early effort on that theme, from some time in the early 2000s:
Simple, yes, but ground-breaking in that the entire advert is based around someone hating the product.
After that, they became far more sophisticated, and developed a brilliant line in spoofs on TV genres. Here they are riffing on the animal rescue programmes:
For a long time, I thought they wouldn't top that. But now, along comes the DNA test reveal advert. This, in my opinion, is simply genius. Here is modern Britain in a nutshell (not that Marmite contains nuts):