Apple AV Lightning Adaptor. Cost in France about 30€.
You will need an HDMI cable as well.
The adaptor fits into your iPhone/iPad and provides connectivity for both the HDMI lead (to the TV) and allows charging as well.
Mine works perfectly on an iPad.
Make sure you get the right version, older iPhones use a different connector. Or if you wish to do it without cables then get an Apple TV and use Airplay.
If you have an Android box you can get an Airplay app that lets you wirelessly send from an iPhone/pad
Cheers, ordered cable from Apple & surprise it's actually I good bit cheaper from Apple Fr than Apple UK. The only drawback is that you can't watch Sky Go as Sky app. Seemingly blocks it.