Must have been leaking a while. When we removed the dodgy joint I found a 28mm compression coupling stuffed into the 32mm mdpe gas pipe. Then some epoxy resin had been smushed around it. What a cowboy.
We worked until gone 8 and it was in some mental storm. I had to drop the pop up gazebo as it was going to blow away. Soaked through to my under pants but got the couples gas line blown through, tested, purged and the boiler on. So they were happy!