We have stopped making bikes with the facility to install an "off road" button as they are both ilegal in the UK and the rest of Europe, I believe Ultra Motor have done the same thing and are no longer producing A to B Metros with the boost button.
Anyone riding a bike that is capable of more than 15.5mph +10% with assistance from the motor is effectively riding an unregistered moped without tax, insurance, MOT and probably without a helmet.
I do believe there is very little chance of being discovered unless a rider is involved in a RTA and the bike is inspected. However I am aware of one such case at the moment and know the police are looking specifically at the top speed of the bike. Unfortunately I don't know what make the bike is, although I have been told it is not a Wisper. If the police discover the bike is ilegal they will prosecute. This will mean a heavy fine, at least 6 points and the possibility of loss of driving licence. The paradox of course is the rider will still be able to ride a legal electric bike!
Even without the "off road" or "boost" it is possible to rig most bikes to break the law. If you are thinking of doing this remember the bike can then only be used legally on private land. for the very little extra speed you will get I strongly recommend everyone to stay legal.
Pedelecs are becoming more and more popular in the UK and we have a very special concession in that as long as Pedelecs are within the law they are one of the only motor vehicles allowed on the road without interference from government.
Let's try and keep negative publicity to a minimum?
Best regards
David