Thankyou for all the suggestions and no problem with router password being viewed, windows are onto totally private courtyard, no pubic access.
Sorry, should have explained, older PC doesn't have wifi, that is the basis of my problem 😉 So when I say wired ethernet needed, only needed to connect the older PC. Can be a wifi to ethernet adapter. I do have a long ethernet cable, can run that temporarily and it may well become permanent!