Help. Shower won't turn off

[figelnarage]

Has anyone any ideas how I get this shower to turn off. This has happened a few months ago but was just dripping and plumber fixed it. Today I can't get it to stop and it's quite a flow.

Picture attached that shows it 'switched off'

Thanks in advance

Sorry I have no idea but bumping for you!

Same thing happened to us on Friday. DH took silver valve off (used screwdriver) and then twisted the exposed copper valve with pliers.

Thanks everyone. DH is on his way home so I'll advise to try the above. Don't want to try myself in case it goes wrong and then I then have to deal with that and toddler bedtime.

Appreciate the responses