bonzobanana
Guru
Illegal under the current regulations, unless the e-assist bike was built before 2016 and came equipped with a throttle then. It doesn't apply retrospectively. And it's not the age of the bike if you're considering putting a conversion kit on a bike built before 2016.
See the thread Throttle on here for more information. Including from a manufacturer who will put it through the MVSA test for you.
The changes to the regulations in 2016 were to get a single standard across the EU. These include the motor size and speed.
You keep writing as if throttles are illegal which they aren't its the twist and go nature of some ebikes that had a throttle. You seem to be confused about the legislation. Ebike kits are not part of the legislation they were overlooked and not incorporated into them they are just allowed or overlooked. The legislation was about factory built complete ebikes. The fact you can have a ebike assessed and allowed to have twist and go functionality is separate from EU legislation. I think this exception was to provide an option for disabled and elderly cyclists and doesn't comply with EU legislation. However such ebikes have to be individually tested which is a stupid process to be honest. Now that we are out of the EU we should just go back to our original legislation which was far superior because it improved safety and accessibility to ebikes.