During his first five nights he was moved seven times. Dogs which are trained to recognise Guzman’s scent patrol the corridors and buildings. All of the security cameras have been checked, and blind spots removed. The number of cameras is to increase ten fold, with the number increasing to 1,000 within the next few months.

Systems which were switched off during his escape – sensors to detect movement of walls or in the ground, and detection equipment in tunnels – have been reinstalled, and updated.

A red alert has been put in place. The floors have been reinforced with three layers of steel, three-quarters of an inch thick.

Given that building work – including with diggers – is taking place around the prison, the authorities have increased their scanning of anyone entering and leaving. Visitors are being screened with a higher intensity, and swabbed for explosives.

Even the vast drinking water pipes which flow under the prison and on to Mexico City – considered the largest civil engineering project of its kind in the world – have been re-routed, to avoid having tunnels under the jail.