Undertaking !!

At a spilt in the road priority, I indicated to the traffic that I'd remain in the right hand lane to proceed straight on at the roundabout in Warwick, UK. The vehicle in the video manoeuvred into the left lane for left turn only traffic, then travelling at speed undertook me and then proceeded to manoeuvre round the roundabout without indication to proceed straight on. Had I or any other road user been on the roundabout or a vehicle emerging from the left onto the roundabout at this point, this drivers illegal manoeuvre would have caused an accident.