Non‐technical summary The inwardly rectifying potassium channel, Kir4.2, is amongst the members of the Kir family of K+ channels whose activity is directly regulated by the external potassium concentration. We show here that, rather than increasing expression of the channel protein, this regulation is accomplished by activation of silent channels already present at the cell surface. Understanding the mechanism of this regulation will aid in understanding the physiological processes in which this subset of K+ channels is involved, such as regulation of blood pressure and control of neuronal excitability. It may also help to explain some of the consequences of hyperkalaemia, or excessive potassium, in blood plasma.