My last job today and the lady of the house says "before you start can I show you something" and leads me to one of their (old aluminium framed) patio doors. She then points out a ten inch long scratch and says it must have been my squeegee that did it. I was a bit speechless to start with other than saying I don't remember doing it. The strange old dear didn't seem to be angling for compo and just asked me to be more careful. When I got round to cleaning it again it occurred to me that the scratch was not consistent with the strokes of my squeegee, it was close to the top of the glass, dead centre and just off of vertical in direction. I pointed this out to the husband who said it had probably been there years and it was the first time she noticed it. I've come to the conclusion that she is one of life's arseholes.