Who actually defines what a high viz jacket is? Is it not reasonable to claim that my uniform bars (mine are white) make my uniform jacket "high viz?"
And in any case, if they spot you not wearing a jacket surely it follows that you are plainly visible?
Anyway, this is thread drift and detracts from warning the unsuspecting that they should avoid the rip off culture of London ****ty, its shambolic immigration procedures, and the intimidating security process.