Airplay mirroring to Apple TV from iPad/iPhone not working

Airplay mirroroing to my Apple TV from my iPad & iPhone has stopped working as of yesterday. Last week everything was fine and I have changed nothing.

My home Network and WiFi seem to be just fine.

I saw that an Apple update in 2013 was the last time this issue occurred, at least according to Apple Discussion pages, so what's happening now?

I have checked Network, AirPort and Apple TV settings, and everything is fine, but the request for Apple TV Airplay/Mirroring on my iPad and iPhone does not stick.

Any ideas please?

Jonny