Quote from police services
“Following on from the increase in burglary across the borough, there is valid intelligence to suggest that people are marking pavements to identify potential targets. Police are asking residents to be extra vigilant and report any instances of this occurring to your local SNT team.
It is vital for any instances to be reported as this forms part of the intelligence building process.”
However Webmaster has done some googling and found some reassurance that the codes may well be harmless notation by contracting services.
An investigation reported on the BBC in 2016 indicated that the true interpretations are :
I might have suggested that we all put “Nothing worth stealing” outside our own properties, but might then find several rather inconveniently placed lamp posts.