Ebikes older than the regs in 2016 can have a throttle and bikes previously used on the road and converted to an ebike can also have a throttle that works to 15.5mph, as summarised by an article on the Pedelecs website:
DfT: Pedal cycles converted to ‘twist and go’ exempt from type approval
When I wrote to the DfT for clarification they replied:
“I believe that the text you have quoted, which has been reproduced on the Pedelecs website, is from private correspondence with the Department for Transport which the recipient has obviously decided to make public. It is not an official document. However, my colleagues in International Vehicle Standards have confirmed that the website has correctly reporoduced their comments and the person writing the website has understood correctly”.
I’ve just converted my Turner with the CYC Photon kit and left the throttle on there.
Howver, I am considering removing it but for the possibillity that it might be useful for those times where you are negotiating a waterlogged/muddy rutted track. Not so useful for using it to try and get started on a very steep bit of track that you’ve made a mistake on and stopped due to the need to have your weight forward anyway – you’re better off trying to peddle due to weight distribution.