A cue-bid is a definition of when you make a bid in suit that you do not necessarily hold. Obviously, most of the time (95%) you’ll be bidding merrily away in suits you do hold, happily telling partner how many points you’ve got, how long the suit is, how suitable your hand is for a No Trump contract - ie all the usual good stuff we’ve been working on.
Sometimes there just aren’t enough suits. Quick, I say! Send out the Butler for more suits! Down to Saville Row with the chap immediately!
Partner opens One Heart and the devilish fiend on your right overcalls One Spade. In a sense, the problem now is not when you don’t have a fit, but when you DO. If you don’t have a fit the options are usually, PASS, 1NT or 2C or 2D. But what if you’ve got a fit and one of these hands?
xxx ............. xx ............... x
QJxx .......... QJxx ........... KQxx
xx ............... Kx .............. Axx
Qxxx .......... Jxxxx .......... xxxxx
With the first hand there’d be nothing wrong with dredging up a bid of 2H. Because of the 1S overcall we’re now in a competitive situation. The polite niceties of what we might/should do in an uncontested auction kind of no longer apply in quite the same rigid way. We have to be more flexible. Our job is now to assist partner in every way we can to find the right level for the contract. At the same time we also have to get in the opponent's way all we can. We might even – occasionally – tell little white lies.
The second hand has better shape and better points. 2H – probably right without the overcall – would now be an underbid in a contested auction, so we have to find another bid and just about all that is left is 3H!
So what about the third hand? 4H might be sound, but you’re relying on partner always having a good opening bid instead of the ghastly mess they usually open with, so what can we do? Bids in Clubs and Diamonds don’t look right and, importantly, would kind of deny the great Heart fit - which is the number one most crucial bit of information you want to get over. Aaagh. We’ve run out of suits! It’s time for that Saville Row moment - the cue-bid!
When the bidding goes 1H - 1S - 2S! the message is this: “I have good support in your suit AND points partner so if you’re rubbish, bid 3H, otherwise bid game.”
The cue bid is the Saville Row bid; it's the posh bid; it’s the extra suit in the wardrobe; it’s tailored; as the Butler says: “It’s all about the fit, sir!”