Andy came out on a Sunday and identified the problem correctly, after an emergency plumber had been unable to find out what was wrong and hence not been able to do anything useful. Andy informed me what was needed, bought the required item and got the boiler going the next day. The boiler needed further repair, which was done a week later, again to my total satisfaction. During the last few years Andy has done all my plumbing work and I have always been very satisfied.