parliament. For those of you who live overseas he was a member of the Senate - our Upper House in Federal politics. He was also leader of "the Greens".
He was there for sixteen years and, I think, most people expected him to be there for another sixteen years. Just recently he spoke about staying until 2024.
Something happened. He changed his mind. He said that, at 67, it was time to go. He said it was time to allow the next generation to take things on, that things had to change.
This came from the man who was seen by many as actually being our Prime Minister. After all, the government needed the Greens in order to form government. They still need the Greens. Brown wielded enormous influence over the Prime Minister. Nobody, except perhaps the Prime Minister herself, would deny that - and even she would have difficulty in denying it to herself.
Brown had immense media power too. If he called a press conference people attended. If he made a pronouncement it got media coverage. He was almost never given the sort of grilling given to Prime Ministers or Leaders of the Opposition. Journalists would only ever try that once with him. They would publicly laud him and privately loathe him.
So, what happened? Did he make an independent decision - or was he pushed? I suspect it was the latter, although it is unlikely we will be told.
Why? He recently gave a speech one night in Tasmania that apparently began "Fellow Earthians" and went on to talk about, among other things, the need for the world to have just one ruling body. That was probably enough. People at last decided his ideas were dangerous - dangerous in the sense that they would lose votes for the Greens.
The Greens will almost certainly lose votes without him. He was the public face of the Greens. He was the person people associated with the Greens. People voted Greens because of him. The only member of the Greens in the Lower House, who holds the seat of Melbourne, is going to find it very difficult to retain his seat at the next election. Only the fact that Labor's primary vote is currently so low can give him any cause for optimism.
But, nothing much is going to change for the moment. When Brown goes in June he will be replaced by another Greens senator, another Tasmanian. This is the way our parliament works. The balance of power is not going to change. The new Greens leader, still another Tasmanian, is going to be just as tough in her own way. She will be a woman dealing with a woman. She has more on her agenda too.
There have been hints of discontent in the Greens. The new leader is the one endorsed by Brown. She has been his right hand woman for a very long time. There were three contenders for the deputy's position. The person chosen is the sole member of the party in the House of Representatives. That may have been done for tactical reasons in the present political climate but it has caused some discontent among those who have served longer.
It is the next election which will tell us which way the Greens are going.