What is "Honorary Lecturer" in the UK universities? I was browsing some UK universities, and I was surprised by the number of 'Honorary Lecturers'. I understand a 'honorary professor' position, normally given to an outstanding scientist outside the academia, but I wonder how a junior academic position (like lecturer) can be given with honorary title.

First, I thought it can be a political figure or something like than rather that someone with scientific achievements, but suprisingly, I found it is VERY popular to fall in this category. 

For example, 10% of faculty members in UCL School of Life and Medical Sciences holds the positions of 'honorary lecturer', 'honorary senior lecturer', 'honorary reader', or 'honorary research associate'.
In this link they explain the subject in detail
In general regarding honorary academic titles for non-employees it is written:


  To recognise the association, the College may confer an honorary academic title on a non-employee during the period of their association.... The title to be conferred will depend on the level of distinction and qualification of the candidate.


And specifically with regard to "honorary lecturer":


  Honorary Lecturer: Must continue in teaching, research or joint industry/academic activity to an appropriately high level