[mycroft]

Vampyr, on 2012-November-05, 13:33, said:

All I could find was this, under "Definitions":

This doesn't at all seem to prohibit an agreement to open with a singleton.

Absolutely. The argument is (and the explanation guide - which has the strength of regulation - makes this clear) that a singleton "generally" - i.e. we know when it will happen, because we have an agreement - is non-natural, and there are no non-natural non-forcing NT openers allowed on the GCC.

[Vampyr]

mycroft, on 2012-November-06, 10:40, said:

The argument is (and the explanation guide - which has the strength of regulation - makes this clear)

Where is this guide? It is not obvious how to find it on the website. Or does it exist only in hard copy?

[mycroft]

Vampyr, on 2012-November-06, 13:05, said:

Where is this guide? It is not obvious how to find it on the website. Or does it exist only in hard copy?

mycroft, on 2012-October-31, 09:28, said:

Given where [jillybean] and I live, the practical issue is the ACBL interpretation of what is a "natural" NT.

I found it by googling "ACBL NT with a singleton"

[Thiros]

I have opened 1NT in the past with 4-4-4-1 hands and a singleton K and consider it a good description. I once opened 1NT with a 4-1-4-4 and a singleton ♥K, and partner drove me to 5♥ with ♥AJ10xxx and what looked like not a whole lot more than a minimum game-going hand. I was fortunate enough to make 5♥ exactly when the ♥Q dropped doubleton.

I would find it less attractive with a singleton Ace since that suit would have no losers in a trump contract, and the singleton K is much better for notrump opposite partner's typical holding. Indeed, I'd rather open 1NT with a singleton Q than a singleton A.