Partner has dealt and he opens 1NT. Your RHO doubles. You bid 2C, which, in your system, is a weak take-out after the double. LHO asks your partner the meaning of your bid and partner says it is Stayman.

LHO passes and your partner bids 2D and eventually, the opponents ended up in 3H which gives them a poor result.

You must ignore partner's spurious explanation of your 2C bid and assume partner has bid according to your system. You must presume and act as if partner has a 5 card diamond suit and assumes 2 diamonds will play better than your 2C bid. You have an obligation to inform the true meaning of your bid at the end of play

if the opponents play the contract (to do so sooner would give unauthorised information to your partner) and at the end of bidding if your side plays the contract.

The opponents have a right to call the Director to claim an adjusted score if they feel damaged by what has happened.

The key point is that you cannot continue bidding and make any use of the wrong explanation given by your partner. You must bid according to your system, even if you commit hara-kari in the process. Even though you know that partner is (wrongly) taking your bid as Stayman in the example above, you are not allowed to compensate. Your bidding must continue to assume that your 2C was a weak take out and that partner is bidding as if he knows this to be the case – under no circumstances may you now adapt your bidding to his reply about Stayman and any of his subsequent bidding.

When your partner gave the wrong explanation of your weak 2C bid, you know that your bid has been misinterpreted and you now have unauthorised information and you must be careful not to base subsequent bidding on this information. The Director is certain to adjust the score if you do.

You are allowed to deduce that a bid has been wrongly explained if you have a cast iron reason for doing so. (e.g.-You open 1NT, partner bids 2D, which you mistakenly describe as weak take out. This gets doubled and partner retreats to 2H, the system transfer response. Everybody round the table can deduce that you have got it wrong and it was meant as a transfer bid. Now all is well unless the opponents can claim that they have been damaged already.

The above is known as a Mistaken Explanation. This is not the same as a Mistaken Bid.

In this case, the partnership system is correct as it is explained. An example will make this clearer :-

You open 1NT and partner, who holds a weak hand with long diamonds, bids 2D intending to sign off. You alert & explain that this is a transfer for 2H, which is a correct explanation of your partnership system. The mistake was in your partner's bid & there is no infraction of Law, because the opponents received a correct description of your system. Your next bid will be 2H and any subsequent bidding in this auction must be made assuming that you are playing transfers. It has now become very difficult for the partnership to find a good resting place.

Partner is in receipt of unauthorised information, inasmuch as he has forgotten the system and then been reminded of it when you alerted, but he is unlikely to be able to make any use of this information. Should he go on to bid 3D over your 2H, then this is a forcing bid showing a game going hand - and not a weak diamond bid. If you pass 3D, then you are said to be fielding your partner's mistaken bid & the Director will adjust the score.

PRD (November 2001) c:\mydocs\rules6