In bridge, should East consider "overtaking" his partner's lead if able?

Question

One example is if West leads a Q (top of a sequence) against a NT contract, and East plays K from Kx to unblock. If allowed to hold the trick, East would lead back the x.

My understanding is that bridge play is designed to protect certain vulnerable holdings, such as tenaces, in the declarer's hand from direct attack by the opening leader, West.

But if the tenace suit is led by East, its vulnerability will be fully exposed. Should East be on the lookout for potential vulnerable holdings in South, and overtake West's lead if an examination of his cards and dummy (and a review of the bidding) leads to a suspicion that South may have such a vulnerable holding? Here is an example of what I mean.

Answer 1

No; overtaking partners honour should not be on East's list of possible actions as dummy comes down.

That is not to say that it is never right for East to do so; or that East should never take such an action.

Rather, there are far too many more important things for East to be studying as Dummy comes down than a check-list of rare and unusual plays. Any such bold action can only be performed confidently through an extremely good picture of the hand, and how the defensive setting trick is to be developed. Such an understanding of the hand will only be hindered, significantly, by spending (need I say wasting) valuable seconds considering a list of circumstances that only occur every one or two hundred hands.

If the action is correct, and one obtains through more efficient means a sufficient picture of the hand to predict this as required to establish the setting trick, it will then become an obvious action.

In the example hand, a count of Hearts and inspection of the Club tenace over Dummy, makes overtaking Partner's HQ obvious. The Heart AJ are both tricks unless Declarer rushed into No Trump with a singleton HJ; and no other Hearts can promote over East's KJT9. If West has HJ alone remaining, the H8 return by East will make clear that a Club return is desired if West gets in again and started with just 2 Hearts.

Answer 2

Yes, East should certainly consider overtaking the lead; thinking is usually better than not thinking. But what conclusion he reaches will depend on the bidding (presumably South has the A if the NT contract was freely bid), the expected layout of the suit, and how many times the defence can expect to get in to lead the suit. Inflexible rules that take no account of what information you have will do more damage to your score than anything except forgetting what is trumps.

Edit: if East believes the Q is from QJ10, it would be sensible to unblock the K; if just the QJ, probably not. But the question as asked is about overtaking in order to tick the box 'lead through a tenace', which is a bad idea, and will remain so even if in this case it (improbably) provides a good result.