This pair do not play Kickback (it was a pickup partnership), but it occurred to me that it's a sequence that must bother Kickback players a lot. In theory 4♥ would be Kickback, setting ♦ as trumps. Or would it be natural, to play? And what about 4♠? Kickback for ♥, or natural?
West said later that she "knew" partner would take 4NT as RKCB for ♥, but bid it anyway (they'd already had a snafu involving a control bid at the four level - they ended up in a 3-2 fit when East passed) hoping to get enough info to ensure the slam was good. "Two with the Queen (of ♥)" didn't help though, as West wasn't interested anything in ♥ other than the ace, and the response left her unsure of the clubs. Note that if she could have bid 4♥ as Kickback, she could have bailed out in 5♦, where here she was already forced to the six level.
I suppose it's a matter of firm agreements. What do you kickback aficionados think?