Thanks everyone. As you say, it is never easy no matter how many times you have to go through it. Cat had a great life, she was spoilt rotten, but made few demands and had no enemies except the cats and groundhogs. She was sick only the last few weeks and while it was a horrible decision to make, we felt confident that she would forgive us for sparing her the indignities and pain she was facing. My clue in the end was that she stopped eating and wouldn't even try the liverwurst she usually loved. With all the dogs that we have had, refusing to eat has been the indication that they were ready to go.
Caroline