When you have the first lead and your partner has doubled a
“no-trump” make, you are expected to lead your highest heart.
Under this system the younger hand does not double “no-trumps” unless
he is willing that a heart should be led; and although the doubling
power of the younger hand is reduced, it makes your lead, unless you
have the misfortune to hold no heart, a practical certainty.
Should you hold an established suit and the ace of hearts you must,
of course, double to have the heart led. When you hold an established
suit of hearts, or a long suit of hearts that can be established in
one lead and a sure card of re-entry, a double may save the game.