Dear Ed & Peter,

I have some doubts about this bidding sequence:

4NT is Blackwood after Notrump is established as suit. A friend of mine says 4NT is slam invitational so the correct sequence is 4NT-6NT (Blackwood doesn't apply).
Another sign-off to 5NT after 3NT: 3NT-5NT.

N/EW		♠	A 4
		♥	K Q
		♦	A Q J 5 3
		♣	A 5 3 2
♠	9 8 5			♠	6 3 2
♥	10 9 8 5			♥	J 6 4
♦	8 6 2			♦	K 9 7 4
♣	Q 9 4			♣	K 10 6
		♠	K Q J 10 7
		♥	A 7 3 2
		♦	10
		♣	J 8 7

Reply from Ed Hoogenkamp ('South'):

Dear Antony,

I think it's useful to play 4NT as invitational in a lot of sequences after a 1NT or 2NT opening bid. Usually there is no need to know partner's number of aces. Take this case: if you can count 33 points you will bid 6NT. Blackwood is pointless since only one ace can be out. If you can count 37 points you will bid 7NT, knowing you have all the aces. So the 4NT and the 5NT bid are free to use as invitational bids for 6NT and 7NT.

Furthermore I would agree on the following in your bidding system in other situations:
- If no trump suit has been agreed on
- Or if the player who bids 4NT had the opportunity to establish the trump suit first (by way of a forcing bid) but has not done so but bid directly 4NT instead
...the 4NT bid is invitational.

Interesting point in this hand is what North should do over an invitational 4NT bid. He has only 20 points but the five card diamond suit improves his hand. On the other hand: he knows partner has only four cards combined in the minors. Difficult. I assume the slam was made because the club lead is difficult to find?

The second part of your question I do not understand well. Do you mean to play 4NT as Blackwood and 5NT as invitational? This is certainly possible, but not necessary as I explained earlier. There is no need to bid as high as 5NT (especially since the occasional 5NT minus one really hurts... :-)

Peter did some extensive answering on a few Blackwood questions on the Dutch 'sister' site www.bridgevaria.nl so he will surely have something to say about it.

Un saludo desde Barcelona

Reply from Peter van der Linden ('North'):

Dear Antony,

Typically Ed: he has copied the juicy parts from my replies to questions on the Dutch site and then says I will have to say something about it as well...
Ok, I will try anyway.

There is a good reason for wanting to play 4NT as an invitational bid as often as possible.
Invitational bids to game are a cornerstone of natural bidding. One of the best known is the 2NT bid:

¹ Invitational to 3NT, but other games are possible as well
(in the European traditional Acol style 2NT directly over partner's 1♣/♦/♥/♠ opening is invitational, 10-11, as well, unlike in the American style where 2NT is game forcing, 13-15)

¹ Invitational to 3NT or 4♠

Why then shouldn't one use the same strong tool in slam bidding? 4NT should play the same part in slam bidding as 2NT in game bidding!
Especially since 4NT as Blackwood is an overrated and often abused convention. In many cases Blackwood is unnecessary, so use 4NT as invitational then.

1. Two examples: 

¹ Invitational to 6NT ('quantitative'), not forcing

South requests his partner to pass if he has a minimum hand and bid 6NT otherwise.
The same principle applies if suits have been bid (e.g. a Stayman or transfer sequence) but no suit has been established, whereas the 4NT bidder could have established it (so he deliberately did not). Ed has already mentioned this.
(If a trump suit has been established, 4NT is Blackwood).

¹ Invitational to 7NT ('quantitative'), forcing

South requests his partner to bid 6NT if he has a minimum hand and bid 7NT otherwise.

By the way, in both examples North can react differently if (!) he agrees upon slam (holding a minimum he will always pass):
- He can show his number of aces after all, on the five and six level respectively (for those who think it is improper bidding a slam without checking on the aces...).
- He can bid six in a suit (after 4NT) or seven in a suit (after 5NT) as a proposal: he shows a five card suit in a major or a six card suit in a minor. South will pass or correct to 6/7 NT.

2. A less clear-cut case:

¹ Reverse, game forcing since South has shown 10⁺ points
² Invitational, not forcing

North has denied a balanced hand. South's hand might be balanced or unbalanced. A quite different situation from the first two auctions therefore.
South could easily have established a trump suit (by bidding 3♦ or 3♥) or propose one (by bidding 3♣) but has not done so. 4NT is a natural bid therefore: South tells his partner there is no fit and he is too strong to bid a mere 3NT. So he suggests 6NT.
In this case the total point count in the combined hands is not precisely known (both players may have revaluated their hand, holding a long good suit). So North might now decide upon slam, while the combined hands hold - say - 30 points only. After all, in view of the long suit(s) twelve tricks might very well be for the taking. But 30 points means two aces might be out.
That is why there is a point in North now showing his number of aces, provided he accepts the slam invitation (if he does not he passes!). Not according to Roman Key Card Blackwood of course, since no trump suit has been established (meaning there is no trump king as the fifth key card).
If North yet wants to suggest a trump slam, he does not reply on the five level (since this would show his number of aces) but jumps to six in the suit he suggests.

Anyway: here too 4NT is not Blackwood in first instance.

En hils fra Orkanger