Problem with Bath/shower tap

[babaduck]

I have an Armitage Shanks monobloc bath/shower mixer tap which switches from bath to shower function by pulling up on a stopper on top of the tap.

This morning, it wouldn't hold so no shower function :mad:

Is there a quick/easy way to remedy this?

 

[Eng Car 1]

Was there any less water pressure today?

 

[AlbacoreA]

Unlikely but make sure the hose is screwed on tight.

 

[babaduck]

None of the above unfortunately. Regular pressure/feed into the bath, but the little pull-up knob that switches the feed to the shower isn't working at all, hence no working shower. It's a complete unit so I can't get at the mechanism. Do you reckon I need to get a whole new tap?

 

[Smashbox]

Perhaps its a washer, in which case I would think you would have to replace the whole unit.