  We present the detection of a bright 3mm continuum source in the Brightest
Cluster Galaxy (BCG) in Abell 851 (z=0.411) with the NOrthern Extended
Millimeter Array (NOEMA). When this detection is compared to other
multi-frequency observations across 21cm-100um, including new Arcminute
Microkelvin Imager 15GHz observations, we find evidence for a relatively flat,
variable core source associated with the BCG. The radio power and amplitude of
variability observed in this galaxy is consistent with the cores in lower
redshift BCGs in X-ray-selected clusters, and the flat mm-cm spectrum is
suggestive of the BCG being a low luminosity AGN archetype. The discovery of
this system could provide a basis for a long-term study of the role of low
luminosity radio mode 'regulatory' feedback in massive clusters.
