Opening Lead?

On Board 10, with everyone vulnerable, RHO opened 1NT, 16-18, and I passed holding

♠ Q J 6 5
♥ K 10
♦ 8 4
♣ A 10 9 7 5

Left-hand opponent transferred to hearts and then rebid 3NT, which ended the auction.  So, what is our lead?

The only thing we can really gather from the auction is that LHO has 9-12 points and probably does not hold 4 spades (else he would have used Stayman) , while RHO must hold exactly 2 hearts.

Clubs are the longer and stronger suit, but in order to set up the suit, we'll need entries.  It is possible that the suit could run right off the top, but not likely (would need partner to hold Kx and declarer to have a doubleton).  The heart King is a possible entry, but again is unlikely, since LHO holds 5 hearts and RHO holds 2.

It seems better to lead a 4th-best spade.  If partner has either the Ace or King, then we set up two or three spade tricks in our hand when we get in with our club ace.  Give partner a trick or two and we can set the contract.  So I lead the 5 of spades and here is what I see:

♠ 10 7 2
♥ A Q 8 7 4
♦ Q J 9 5
♣ J
          ♠ Q J 6 5
          ♥ K 10
          ♦ 8 4
          ♣ A 10 9 7 5

Partner wins the Ace of Spades and plays back the  8, declarer winning the King.  It seems declarer must have only 3 spades;  holding K943 she likely would have ducked around to the 10, preserving the K9 to protect against my Q6.  So, either she has made a mistake or she doesn't want to lose the lead and have us switch to another suit (probably clubs! drat!).  She then starts on diamonds, taking five tricks in the suit.  So, declarer holds 5 diamonds, 3 or 4 spades, 2 hearts, and 2 or 3 clubs.  She then plays the Heart Jack.  I must cover this with the King, else she will let it ride and then finess my King to win 3 tricks in the suit to get to 9 tricks.  I am hoping partners 4-card heart holding includes the 9, or the entire suit is running anyway! 

Indeed, partner does hold the 9. As the cards lay, declarer could still make the contract by leading the Club Jack from dummy after taking the top two hearts, eventually coming to 5 diamonds, 2 hearts, 1 spade, and 1 club after forcing out my Ace of Clubs.  However, she continued hearts, and only came to 8 tricks.
 
                   ♠ A 8
                   ♥ 9 6 5 3
                   ♦ 7 6
                  ♣ 8 6 4 3 2

♠ 10 7 2                            ♠ K 9 4 3
♥ A Q 8 7 4                     ♥ J 2
♦ Q J 9 5                          ♦ A K 10 3 2
♣ J                                   ♣ K Q

                  ♠ Q J 6 5
                  ♥ K 10
                  ♦ 8 4
                 ♣ A 10 9 7 5

We ended up getting a top board for setting this one trick.  Deep Finesse says that with perfect play, only 8 tricks are all that is possible.  It seems my spade lead was ill-advised afterall.  If I had led a club, any club, at trick one, then declarer can only get 8 tricks: 1 Club, 5 Diamonds, and 2 Hearts.  The old maxim of leading from your strongest and longest suit works pretty well.  We were lucky here...I should have followed it.