ITV and eCall system

I have been reading that cars now need an eCall system for 112 emergencies to pass an ITV, and that cars prior to March 2018 may not have this.

Does anyone have any information on this?

Thanks

Compulsory for new car models
If you buy a new model of car, approved for manufacture after 31 March 2018, it must have the 112-based eCall system installed. This rule applies both to cars with no more than 8 seats and light commercial vehicles. If you have a car which is already registered, you are not obliged to retrofit an eCall device but you can have it installed if your car meets the technical requirements.

Great, thank you.