Blah, went to upgrade the router. Thought I knew my password.
But when you upgrade, you lose the web interface, and you have to sign in with ssh to get it working. Didn't work and I went gonzo. None of the 'failsafe' mechanisms work. You can't do a factory reset. Doom!
Wait a sec, I had to do ssh with -l root Duh!!!! Then I could get in... phew.