So, that #Waterman fountain pen I bought for my mother shortly before Xmas 2007 that never worked properly...
...I managed to find it a week ago and I've just spent a couple of hours cleaning it very carefully. It must have had some dried ink from factory testing blocking the flow, because it now works perfectly!
And I've been able to identify it as being part of their #Hemisphere range. They still make the range, but not in this lovely dark, rich, metallic red.