Fortunately everything is backed up to two external hard drives so this is more annoyance than catastrophe.
Very odd. I plugged the Lenovo into a different outlet and why it still isn't working, at least the BIOS sort of starts. Not enough battery? After an hour plugged into a known good outlet the Lenovo can at least run BIOS diagnostics. But there is no hard disk diagnostic: hard disk not responding?
Curiously, my wife's Toshiba Portege is making bad hard drive noises and refusing to boot. Ever wondered what different hard disk noises mean? See here. At least I know what this is: just order a replacement hard drive, maybe SSD to boost performance.