Left the cool of the loungeroom to prepare lunch. Kitchen floor was very wet. Turned water off at the meter outside after determining the source of the leak. It’s the now unused filter tap supply line, a narrow polyethylene tube.
I cut it away from the sink fitting , bent it in half, crimped the bend which I then held in place with cable ties.
Mixed up some 5-minute set epoxy putty, forced some down the tube & formed a blob of it over the cut end. I let it cure for 10 minutes & turned the water back on.
Pleased to report the repair is holding.