I have a headcanon that Arthur’s not the kind of guy for hugs and physical affection and whatnot, and so whenever anybody hugs him he practically hisses and acts like he’s being strangled. People do it anyway, like. But there’s one guy who he desperately wants a hug from - the dude he likes, Alfred. Except, he can’t ask for one, because that would be OOC and would raise suspicions. And Alfred’s learnt to respect his boundaries, so there’s no chance of a spontaneous hug. Even at Alfred’s birthday where he’s hugging everyone, when Arthur writes something in his card that makes him really happy Arthur’s there like ‘YES HE’S GOING TO GIVE ME A HUG’ and he’s all excited inside…
Aaaaand Alfred gives him an affectionate pat on the head, saying 'I know you don’t like hugs, so I shall give you a pat!’.
Arthur is crying inside and cursing himself for enforcing those boundaries so emphatically and he’s pretty sure his grin is more of a grimace as he accepts the head pat.
Because of course the one dude who respects his no-hugs policy is the one dude he wants to pay it no heed.