Well I went around for the old gits 85th birthday & had a look. (wine had been taken, so it wasn't a thorough check)
It boots up & gives you a password prompt but if you try to put a password in it wouldn't take the letters & you just got the spinning beachball.
Going into single user mode worked, I got a load of diagnostics, File System Check said it had been modified. I ran this again and then rebooted , this time it let me input the password , but still gave me the spinning ball.
Holding down the Alt key on startup took me to the disk health utility, I used the first aid option to look at the drive , but it's still the same result.
He's not got a backup , but barring his porn collection I doubt there's anything irreplaceable on there. What next ? (my 2008 machine has been totally reliable, so Ive never had to get down & dirty with it)