Can't disable screen mirroring on iPad pro. Screen Mirroring widget is unresponsive

I have a new iPad pro 11 inch 2nd generation and an iMac, which is running on Mojave 10.14.6.

I've noticed my iPad mirrors the screen on my iMac and I'm not sure how this happened because I didn't set up screen mirroring on either device.

I'd like to disable screen mirroring on my iPad because my iMac is a shared computer, however I can't see how to do this on the iMac.

When I try to disable mirroring on the iPad I go through control centre to get the screen mirroring widget but this is unresponsive and spins round (see attached pic).

Can anyone advise how I could disable mirroring on my iPad?

Thanks