If you
are doing a radar approach (SRA or PAR) you will be talking to the radar
controller but he doesn't control the use of the runway; that's the job of the
tower or local controller.
The two
controllers will be talking to each other and if the tower controller has not
given a clearance for you to land by the time you have reached 2nm from
touchdown the radar controller must instruct you to carry out a missed
approach.