A mounting for a support post of a safety system has a cylindrical stem to be removably received in a cylindrical socket of an anchor device to be secured to a structure, and a connector enabling connection to the support post of the safety system. The connector is articulated with respect to the cylindrical stem to be adjustable over a range of attitude orientations with respect to the cylindrical stem and a securing device secures the connector at a specific attitude orientation with respect to the cylindrical stem. The mounting may be used in a safety guardrail system for working at height, with a vacuum anchor and a support post to which the guardrail is mounted. The support post is mounted to the vacuum anchor by the articulated mounting to enable the orientation angle of the support post to be adjusted with respect to the anchor device.