By Polly Hudson This is, of course, the news nobody wanted to hear, the diagnosis no-one wants to receive, but outweighing all that, having to tell your children is every mother’s worst nightmare. Working out how to explain things to them must have been agony for poor Kate. Pitching it appropriately for their different ages, attempting to be just the right mix of honest and comforting. Trying to prepare them for the road ahead without terrifying them. Reassuring them – as she will have done so many times, about so many things – that it’s going to be OK when she must be extremely frightened her…