My triton shower will not stop running!?

I have a triton T80Si shower, it has always run without problem, however, the water supply was recently turned off for plumbing needs, when it was turned back on, there was probably air in the system as initial spluttering of shower with air spluttering sounds etc. But I can not now stop the water flow.

It still works, ie heats the water, however, even when switched off on the on/off switch and turned off on the power pull cord, water still flows freely through the shower!