The White Van
Being suspicious of the unknown is probably a good thing, but "The White Van" maybe going too far!
In this context the "White Van" could be any colour but the driver and cargo are unknown. The vehicle could be a delivery van or simply privately owned, but it is not known to the person or persons that spot it in their vicinity. The assumpsion is the the drivers or occupants are "up-to-no-good" and the community needs to be made aware of them!
An example of a "White Van" post from Facebook:
17 Dec 2020
A reply/comment
The following should be on the History of the Village Facebook page page.
Yarnsmith is in Belchamp Walter. The post was made April 2 2014 - the friends Facebook page was setup 25 July 2013
·This looks like blatent advertising to me! Not that it was stated that this was not allowed but considering that not averyone could post on the Facebook page at that time it seems a bit self-serving.