Assuming your friend arrived on time for his appointment and there is no reasonable circumstances for the two-hour wait (i.e. emergency call-out) then I suggest he makes a formal complaint, the way to do this is look up the appropriate authority in the phonebook. Leaving a surgery can be difficult as it won't be easy to get on another doctor's list, so he must approach the problem head on and get answers.
I don't know what your surgery is like, but in mine there a few very popular doctors who you have to wait weeks to see, so the next time he makes an appointment it may be wise to just see any doctor who is less busier than others, at a time when the place isn't likely to be jammed.
It is frustrating sometimes, I know. Trust me I'm not a doctor.