I have an elderly relative who I fear has the early stages of dementia.  This is sad enough, but she has a very dominating  boyfriend who I recently discovered is married.  He has become far too involved in all aspects of her finances and day to day life, but will not back off despite me having confronted him.  She is very domineered by him and is pushing me aside more and more.  I have power of attorney, but don't know what to do next. Any advice?

You have probably been informed of this already but just in case: I have heard that there are organisations who deal with what is called "financial abuse". If you do a search using google.co.uk you can find what they do and where to find them.