For those of you who can't remember, the last Agency of the Decade was called HHCL (and I was the second "H").
And for the benefit of any agency in the running for this most prestigious of poisoned chalices, allow me to tell you what I think did happen.
We let the original dynamic of the partners dissipate. In other words, we fought too much. This came about through politics and envy. If, in your agency, the original partners are still working happily together, you're probably OK.
So my advice to all partners in all agencies is this - see if you can stick together.
It's weird - there were all sorts of personality differences between us, but they got subsumed when we were young and struggling. However, as soon as success came our way, we fought like cat and dog.
One of the partners in particular was always trying to get other partners off on "sabbaticals", which effectively undermined them in the agency. It was like Big Brother, with slightly more at stake. In fact, it was terrifying.
As a result of these feuds, we eventually fell foul of "Bogle's Dictum" - the mantra that any ad agency is only three telephone calls from disaster, ie. if your top three clients decide to leave at the same time, you're pretty much f*cked.