A similar thing happened to me, in that an ex colleague wrote to my managers slagging me off (she had been sacked for incompetance (not by me) and was bitter basically. But I felt like you, how can a person just be able to say bad and untrue things about you and you have to let it lie? I was fortunate in that I am still working and in a union, so I asked them, basically because she had written it down it was libel. But this is a very expensive case to bring and also to defend, I was prepared with the union solicitors (not my own money) to do this, but my managers and HR dept wrote me a letter for my file saying they didn't believe her slanderous comments. So I felt that this justified me letting it go, knowing that all my colleagues knew the contents of the letters. But I know exactly how you feel and would definately get a solicitor. Or even ask for a meeting and confront them with it, don't end up spending money on fighting it, try and negate the slander in another way.