After many conversations with DVLA/HMRC it now appears despite what the form says that you do NOT need insurance to register a trials bike for road use. You DO however, need an MOT, proof of purchase/age and when it was imported literature etc.   NOW you also need it to be registered with the HMRC on their NOVA database. This cannot be done online and you have to telephone them on 0300 200 3700 for a nova1 form. I'm only putting this on here because the DVLA info is scant. Be warned that phone