We had our registration number likewise before it was stolen. In the subsequent 2 years, no one has reported noticing it. I subsequently found out that it has to be crosswise, not lengthwise, like this, to register on motorway cameras. But if anyone has found WX16HCA on their roof, please report to the police. They'll probably ignore it,I have our van registration number on our roof in case the plates are change if it does get nicked.
Bought my large self adhesive ones off of eBay.
View attachment 889564