  We report on the coupling of a single Nitrogen-vacancy (NV) center in a
nanodiamond to a fiber-based microcavity at room temperature. Investigating the
very same NV center inside the cavity and in free-space allows to
systematically explore a new regime of phonon-assisted cavity feeding. Making
use of the NV center's strongly broadened emission, we realize a widely
tunable, narrowband single photon source. A master equation model well
reproduces our experimental results and predicts a transition into a
Purcell-enhanced emission regime at low temperatures.
