We know that he is (or at least intends to) but we don't quite know why.
The key to staying is to want to do something with the 12 months that are left. At the moment I have no sense of Brown having an ambition that is the measure of the situation. He tends to view minor tinkering as being crucial and vital reform.
Time to look to the bigger frame of history and actually do something brave with the next 12 months.
I am afraid that this does include a Bill of Rights, reform of the Lords and PR. Now or never.