A Dutch onshore gas well was drilled to a total depth of 5136m along hole (3700m true vertical depth) with a maximum deviation of 89 degrees. The well was completed with 7 5/8" 13 Cr tubing with a 7" cemented liner across the reservoir providing full bore access to the pay zone. Due to the very stratified nature of the reservoir the long term sustained production depended on achieving vertical connectivity with all the layers. In order to achieve this and to maximise productivity a 1 run underbalanced perforating operation was required. Due to coiled tubing limitations in this deep, high pressure well a Hydraulic Workover Unit was selected to deploy and retrieve the guns. A total gross interval of 1026 metres was perforated in one run utilising 3 3/8" deep penetrating guns and thereafter snubbed from the well under live conditions (460 bar at surface). To date it is understood that this is the longest section of guns conveyed, fired underbalanced and deployed out of a live well. This paper addresses the perforating technique selection, the planning and execution process, the major operational learning points and discusses final productivity results which demonstrate the validity of this technique.