When the pumps which pressurise the irrigation system fail to automaticity switch to stand-by mode it generally indicates there is a leak on the system. After hunting around the course looking for possible signs it was thought it was the wet area to the side of the 16th tee. After isolating the irrigation to the tee the pumps still refused to switch off, thus suggesting this was not the problem.
The leak was eventually found on the mains supply which leaves the pumphouse. This part of the irrigation system is fitted with galvanised steel isolation valves and one has a rotted hole on the side. This will now require digging out and replacing to get the irrigation system back to full working capacity.