A bacon and avocado sandwich

I went into a decent-looking “Italian” sandwich shop for my lunch where I asked for a bacon and avocado sandwich. I interpolate that the ingredients were there; the avocados were nestling on the counter; the bacon was sizzling backstage. However, my request was refused, on the grounds that the sandwich in question wasn’t on their list and the server wasn’t “allowed” to sell it to me unless it had a corresponding button on the till. She was apologetic but ultimately unhelpful. So I went next door to the greasy spoon which I suspected would give me the same look they gave Peter Mandelson when he asked for some of that “delicious-looking guacamole” in a fish and chip shop in Hartlepool. But I was wrong: they had bacon; they had avocado; and they made me the sandwich for which I had asked at, I suspect, half the price the earlier place would have demanded if they had been prepared to sell me what I wanted.