The degree of friendship is not defined, so no difference is made between a friendly acquaintance and a close friend of long standing. When assessing whether a gift is admissible, what criteria are used to define who qualifies as a friend?
Personally, I have a friend I've known since I was 14, Charles, and I say hello to him in passing. Even if we haven't seen each other in 40 years, he remains a friend, because there are some things that stay with you.
You have to consider the cultural aspect and the specific circumstances of travel with friends who also have a business relationship with the government. In those circumstances, it is possible that the conversation might take a turn toward work-related topics. In any case, only one person makes the decision concerning the admissibility of a claim, and that person is you.