We did weaken in the end.  We had decided that our kids should not be poisoned by video games and the likes.  Much better for them to play healthy vigorous games and to rad.  But Joey can't really read by himself yet and it is also true that it keeps him a bit out of the loop when all his mates have it.  So, after a period of good behaviour, and him sort of playing it on Youtube, or at least becoming familiar with it, we bought Mindcraft for him and put it on the I-Pad.  He was delighted and agreed to certain conditions re the amount he can play.  It seems to work and he respects those limits - and is clearly motivated to stay in our good books to enable continued access!  Putting it on our I-Pad also means that it is not 100% 'his' and he knows that it can be deleted at any moment.  Fingers crossed.

On the positive side, he was really excited about going to school today, and in great form.  Why?  So that he could tell his mates all about it!  And not just his mates but also Ryan, his nemisis!