Oxford Big Boss Alarm Lock (Oxford OF4) Thatcham Approved Vehicle Security (16mm version). This is part of my lock system I use at home to secure my bike, All three parts (Anchor, Chain and Lock) are from the same known brand “Oxford”. Unlike my other 2 parts this comes with a Thatcham Approved rating which does reduce your insurance, unlike the others which are Sold Secure. After my issues with my original lock, I decided it was worth investing in something that would not only give the highest strength Oxford offered in locks, but it was also an alarm system …