Assuming that South takes the diamond double to show long diamonds the line he took works whenever West holds the DQ. In view of the Diamond double it seems to be the better choice (more than 50%). Karoly's line is better if South plays East to have 2+ diamonds.

Francis Glassborow, Oxford,

Aren't you both right?
After QC there are three entries to dummy (as south needs to set up the diamonds) but after AC there are only two. In the column it says that declarer cashed AC before moving to diamonds but clearly there was no obligation to do so.

James Handscombe, London,

No! After winning the CQ, South can lead DAK throwing a spade. Then diamond ruff, heart ruff, diamond ruff, heart ruff, cashing.

Karoly kelen, Budapest, Hungary