Translation: My first position at Bath was technically a UK old-university Lecturer B. For UK "new universities" (former polytechnics) the same position is called "Senior Lecturer". This is roughly equivalent to a USA assistant professor, except that my contract has always run through August of the year I turn 65.  (That is, no tenure issues.)   UK lecturers hold grants, have PhD students, develop courses, etc.

I am now Reader, which means I went through a process much like tenure involving letters from external academics etc. Getting promoted to Reader in the UK indicates that you are very strong in research and are expected to become a full Professor. Lecturers can also get promoted for their teaching and administration: in old universities that position is called Senior Lecturer and in new universities it is called Principle Lecturer. Often people are promoted for their teaching first and then subsequently "translate" to a Readership in anticipation of applying for a chair, but I skipped that step.

I am very glad to be a Reader now so that people familiar with the American system (or UK new universities) just have no idea what I am, rather than thinking I'm something I'm not.