I spotted this on several aluminium columns outside the Oval cricket ground in London at the weekend.
At first I thought the "non standard root installation" meant they had offset or flanged roots due to utilities in the way. However, when I read the notice again and looked at the base of the column, I realised it was a case of "elf and safety" gone mad - once again.
The columns in question, are crash safe types mounted in socket foundations, so yes if the column is crashed into by a vehicle, it is designed to separate at the base, but surely if you are in the vicinity of such a crash, then I think a lamp post falling over is the least of your worries. The column is not going to collapse on its own accord, which the notice seems to imply.
Just to add to the ridicule of it all, the road in question has a 30mph limit, next to the columns is a bus lane, which actually terminates in a few hundred yards, meaning the traffic speed will be much below the limit as the buses need to merge into the main carriageway, and overhanging trees and the column set back from the kerb, means the buses are probably a metre or more away from the columns anyway.