I am very grateful for all your kind advice and support, and to have found this forum where I can vent. In the end we went out with our son, other two adult children and some of his friends to celebrate his birthday last night, first in a restaurant then in a pub. It was a good evening, but a certain amount of discussion was around the mind-blowing news he'd shared with me in the morning (when I popped over to deliver card and cake).
I am shocked on so many fronts. Foremost, that our son (on all other levels, intelligent, clever, an entrepreneur, but always a risk-taker and has had some sticky moments in his life - so perhaps not totally surprising) could allow this situation to happen in the first place - by his own account, a one-night stand, far away. Why no protection, on an STD level let alone potential for pregnancy?? Questions about our upbringing of him. The morality of what he did (or lack of it), and the very far-reaching consequences of his actions.
The lady concerned comes from an extremely different culture, religion and ethnic background, they hardly speak each other's languages, and he cannot pronounce her first name! (laughable in any other situation). The "delicate" question raised above about his paternity is going to be checked once the baby is born - due end of next month, so we don't have much time to adjust to this. He is taking it all very seriously, is arranging and paying for good medical care for her, discussed DNA testing with medical authorities over there and here, and spoken to the British Embassy there about the child having a passport. If the baby is, as he strongly suspects, his child, then he will support the mother financially, and would like him (it's a boy) to go to the international school there, and possibly bring him over here for secondary education. All far, far down the line, but it's good to know that he's planning.
For OH and me, all the questions of bringing a child into the world of mixed race, who may have issues for that reason in both countries. He will be loved by us, but the problems he may face about his origins may be huge. And not the exciting start to being grandparents that we had anticipated, nor the timing - I feel far too "young", even thouogh many of my friends are already grandparents, because I recognise my children aren't yet ready for the responsibilities of parenthood; but he said to me last night, he is "strapping himself in for the journey", and he will, I'm sure, do what he has to do for his son.
Now a waiting game for the birth. My daughter said very sensibly, "Let it all settle". Once we have the result of the DNA test, we then need to take it forward. How much involvement we shall have in this baby's life remains to be seen. It depends on so many factors - the mother, especially. I would go and visit her and the baby, but OH has already said he doesn't want to. Also, OH and I both have mothers in their late 80s, and it's how to broach this with them, too.
I've hardly slept all night, and now face a day at work (teaching). Strong coffee now. Very many thanks to you all for your interest and support.