how to dismantle monobloc mixer tap?

My cold tap only is leaking. It dribbles out from the cold water handle area. I need to know how to take apart the tap to fix the issue (probably a washer). It's not immediately obvious however, how exactly to take it apart. The make is Bongio and it looks very much like this one http://www.tapstore.com/media/technical-pages/Images_help_pages/ro_bas_c.jpg