Good buddy of mine used to work Heathrow security, and now trains airport security staff globally. The siruation for drugs has (unsurprisingly) changed massively since 9/11. His view is you’d be very unlucky to get caught with a small amount for personal use on your person. The scanners don’t pick it up, the manual security wands don’t pick it up - they’re both looking for explosive traces and metals. Hold luggage - be wary. Much higher likelihood of either getting randomly searched, or a dog latching on to something.
The dogs are now trained to detect explosives. Apparently (and this was a surprise to me) they can’t be taught to sniff for multiple things - it’s drugs OR explosives, and given the change in priority 20 years ago, they’re trained for explosives. The Heathrow dog training company tried to have them cover both years back, and their tests returned a way higher number of false positives and false negatives.
However, it’s still very possible a dog might just smell something weird in your bag (½ kilo of White Widow skunk for instance) and if your bag gets pulled for a check, you’re fucked.
