As I've already said earlier in the thread, this is what I did after I learnt the term from Rob Morley. Often Googling doesn't help if you don't know the right word; I would have called it a "spur" by analogy with adding an extra mains socket :-)
In Windows 8 all I did was to go to the Network and Sharing Centre, choose "Change Adapter Settings", select the 2 ports (referred to there as "Ethernet" and "Ethernet 2") by Ctrl-clicking on them and then Advanced > Bridge Connections. And, er, that was it.
It took effect immediately - no need to reboot or touch the RPi at all. Both machines have been rebooted since and it still works perfectly - absolutely delighted.
Another Dave