Girling brakes in the wet

[Peter Naulls]

Over the past couple of years I've noticed the brakes on our Ruby occasionally pulling to the right quite badly in wet weather. When it first happened I assumed it was water in the nearside drum but it has got progressively worse. This morning I drove to work in the dry and the brakes were balanced fine, On the way home it was very wet and it seemed quite clear that the nearside front brake was having little if any effect.

I've removed the drums and the linings look to be matched. The balance quadrant for the cable is free to move as it should and the levers are both roughly vertical when applied. The tyres are matched and both at the same pressure. What am I missing?