A civilised relationship requires two consenting partners - and the right to change one's mind.
People in Northern Ireland have several times been asked if they wish to remain in Union with Great Britain, but no one has ever asked those living in mainland Britain if they want to be in Union with Northern Ireland. This may well be because they would say "No".
I would say "No" if I was asked. I can't think of any good reason to go on subsidising this loss making subsidiary of Great Britain. I have never been there and I don't feel I have very much in common with the people who live there. As far as I can see, it would make much more sense for Northern Ireland to federate with the Republic of Ireland with which it shares a history, a lot of culture and an island.
Of course, I realise that the people in the Republic of Ireland may also not want the North. Right now, they are not in a position to take on a loss making subsidiary. They are no longer as conservative as they once were and they must surely hesitate to involve themselves with so many political and religious reactionaries.
Great Britain pays the price of its Imperial past in peculiar ways. Most importantly, the tail now wags the dog.
If Argentina invades the Falklands again, then British taxpayers will have to fund an expensive war to retake them. They will have no choice in the matter, for sure. Only the Falklanders are asked whether they wish to remain British. Well, of course they do. We pay the bills - the garrison we already maintain there is way beyond anything the few thousands Falklanders could afford.
And if the Peace process in Northern Ireland breaks down, it is mainland British politicians whose energies will be absorbed in trying to sort it out and mainland British taxpayers who will pay the bribes necessary to separate the feuding communities.
It was not ever thus. When Britain had its back to the wall in World War Two, Churchill did nothing when the Germans invaded that other offshore liability, the Channel Islands. They were left to their own devices. By and large, they got on well enough with the occupiers. It was a great period for local stamp collectors.
And it was Churchill who in 1940 authorised an offer to the Republic of Ireland which would have set up a joint body to begin "at once to work out the practical and other constitutional details of the Union of Ireland" in exchange for Eire's immediate entry into the War on the allied side. (For full details, go to www.winstonchurchill.org)
Of course, Mr Cameron is not Mr Churchill.