I have a double 2 way switch. One of the switches operates, together with an upstairs switch,the light on the landing.Works perfectly well. The other switch is installed as an off/on control for two wall lights in the downstairs entrance hallway. It used to work. I can not remember if more work has been done in the house in that area but I do know it does not operate correctly now. When I use L1 and the common as the terminals the lights stay on permanently, When I use L2 and the common the lights will not work at all. A bathroom fitter happened to be in my house one day and mentioned that he had served his time as an electrician and confidently said that I had lost the neutral. He did not have the time to expand on that and was gone. Was he right and if so what does he mean and how do I correct the problem. I would be grateful for any advice on this matter.