This is taking the biscuit.
Way into work: unplug Powerbook from PSU, bundle up PSU. Work on train a bit. Get to work. Plug PSU into power socket. Plug PSU into Powerbook.
No light on charger ring; no indication of a charging battery.
Change the fuse, same problem. I think, after two and a half years, the PSU is dead. Investigate buying a new one. A new power supply will be
I give up.