Roman Keycard Blackwood
I'm sure you're all familiar with Blackwood; for better or worse, it's one of the first conventions beginners learn. When contract bridge was still in its infancy, Eadsley Blackwood observed that slams missing two aces don't play very well, and came up with the idea of counting aces during the auction. Figuring that 4NT was a very underused bid, he chose to use it to ask the question "partner, how many aces do you have?"
Since then, people have tried to build a better mouse-trap in a variety of ways. Roman Blackwood was developed by the Italian Blue team, and is "the eleventh worst convention ever", according to Toby.
The much more useful Keycard Blackwood was born of the observation that slams missing one ace and the king of trumps are pretty bad too. Its solution is very simple—it just counts five "aces" including the king of trumps. The only issue is that sometimes it may not be clear what trumps are.
From there, we go to Roman Keycard Blackwood (RKCB), which is played by almost all of the experienced university pairs. It is a modification of Keycard Blackwood, so again you need to know what trumps are. It may be worth only using RKCB when trumps have explicitly been agreed at first, but I think a jump to RKCB agrees the last bid suit as trumps (see below). As before, 4NT asks, and the replies are
Let's go through this in detail, assuming 1430 RKCB, with hearts as trumps.
The reason we play 1430 is that if the trump suit is hearts, as above, and the response is 5, you can ask for the queen and still stay out of slam if partner doesn't have it. If the response is 5, you can't. You tend to want to do this when partner has one keycard, not when he has none, so it makes sense to swap the responses.
I recently played in a Cambs + Hunts league match against a team from the Cambridge Club, partnering Jon De Souza. We won by 57 IMPs, and were helped along by two boards where RKCB allowed us to find out that slam was good. As you can see, on one of these it was vital that we were playing 1430.
|Example hand #1|
|The slam can be defeated double-dummy on a diamond lead, but East led a spade. Jon won with the ace and knocked out the ace of trumps. When trumps broke 3–2, there was no difficulty in ruffing a club for his twelfth trick.|
|Example hand #2|
|After drawing one round of trumps, I played the T, which was allowed to hold (if East covers I can draw trumps and cash winners), then crossed to dummy in trumps to play hearts, pitching diamonds. Eventually a heart was covered, ruffed and overruffed, but at this point I could claim on a crossruff.|