bluejak, on 2011-September-28, 09:26, said:
There are two sorts of 'impossible' bids.
First, those without UI where partner makes a serious effort to guess what his partner is up to, but generally assumes they are natural.
Second, those with UI where partner takes advantage of the UI and then argues vehemently that no other call was possible because the bid was impossible.
Moi, a cynic? Surely not.

Well since you ask.....
I do recall a couple of years ago (at Brighton) falling a victim to your cynicism.
LHO opened 2
♦ showing, if I remember correctly, a weak hand with
♦ plus a 4-card major. Partner doubled (for take-out) and RHO bid 2
♥ (pass/correct). I bid what I intended as a natural 2N, which partner alerted (oh dear) and bid 3
♣. Now the UI told me exactly what was going on - partner had decided to treat 2N as Lebensohl, as it would have been over an ordinary weak 2 and a take-out double if responder had simply passed. But of course I had to try to decide what 3
♣ over a natural 2N would have meant, and (despite your cynicism) I made a determined effort to do so. I'm not sure I found the right analogous position, but in general we play 3
♣ as Baron over most natural 2N bids in either contested or uncontested auctions, and this was the best I could come up with. I think my shape was 3343 - certainly I didn't have a 4-card major, but I did have 4
♦. However, bidding 3
♦ didn't seem to make much sense when LHO had already shown
♦s, so I thought I could try to emphasise that I had good
♦ stops by bidding 3N.
Unfortunately, this ran into the Bluejak doctrine of Unauthorised Panic, since repeating an intended natural denomination at the lowest level is the standard UP response to a system misunderstanding. Instead you ruled that 3
♣ could have been natural and passing it was a LA. I remember thinking at the time this was very unfair since if it was natural it was surely a strength-showing bid too strong for an immediate overcall of 3
♣ over 2
♦, and therefore there was no way I would pass it with decent values - indeed I would almost certainly bid 3N! (In the event, the AC agreed that 3
♣ would not be passed, but ruled that 4
♣ was a LA to 3N even though it was pairs scoring.)