1570 J. Foxe (rev. ed.) I. 205/2 A certayne great beame or masterpost was losed out of ye place.
2004 Re: Roc Master Posts in uk.rec.subterranea (Usenet newsgroup) 19 Apr. I am reliably informed that Master Posts were chosen by British Telecom who indicated which Post in the Cluster was most ideal from their point of view in relation to land-line length, strength of signal etc. etc.