While I do not work for BA or any other airline customer facing role, if I was the recipient of an edible / drinkable gift from a passenger I would likely discard it given the obvious safety implications of not being able to verify where it came from or that it had not been tampered with. If someone wanted to harm individuals, a very easy way to achieve this would be giving staff tainted "gifts" to consume and you can imagine how bad the situation could get if a large number of CC were incapacitated mid flight by "gifts".