MONITORING PLACES OF DETENTION : A PRACTICAL GUIDE 37 For a long time, monitoring at the national level was based only on inspections carried out by internal administrative bodies. But the necessity to have a broader public scrutiny of places of deprivation of liberty was more and more recognised and other forms of national monitoring emerged, totally independent from the detaining authorities. In parallel, the idea of international control was also developed and monitoring places of detention by international organs slowly became a reality. With the recent adoption of the OPCAT, based on preventive visits to places of detention by both international and national visiting mechanisms, a further step was taken towards establishing a global system of mutually reinforcing international and national mechanisms. It is also important to note that with the adoption of the OPCAT, for the first time in an international instrument criteria and safeguards for effective functioning of national visiting mechanisms are set out. Sections 1 and 2 of this chapter provide an overview of the types of existing mechanism at the domestic and international level respectively. Section 3 sets out the visiting mechanisms foreseen in the OPCAT, with special reference to the national preventive mechanisms. Finally, section 4 deals with the question of the necessary coordination between domestic visiting bodies, and with international visiting bodies. 1. VISITING AT THE NATIONAL LEVEL Monitoring detention conditions is, above all, the responsibility of the national authorities in charge of persons deprived of their liberty. “In order to supervise the strict observance of relevant laws and regulations, places of detention shall be visited regularly by qualified and experienced persons appointed by, and responsible to, a competent authority distinct from the authority directly in charge of the administration of the place of detention or imprisonment." Principle