NORTH
 AT64
 AQ
 T86
 AT74
 QJ53
 K7653
 Q3
 32
   8
 JT92
 KJ7
 QJ965
   K972
 84
 A9542
 K8
Dealer: North    Vul: Both   MP Scoring

West

Pass
Pass

North
1
2
Pass

East
Pass
Pass
Pass

South
1
4

 Trump Promotion 

West led what looked like a 4th best heart.
Dummy's Q won and there appeared to be just two diamond losers if trump divided.
A 'safety play' looked possible: Win a top trump and play toward the other hand's 2nd highest trump.
How does one choose after just trick one which of the opponents is more likely to have the spade length?
North South held 4 hearts combined, the outstanding hearts being:
KJT976532
One of the defenders would have at least 5 hearts and the other at most 4.
Which hand was more likely to have 5 or more?
If West had led the 2 playing 4th best leads, East would have at least 5 hearts.
Then West on average would have more "vacant spaces" or non-hearts in which to hold spade length.
If leading the 3, West might or might not have a 5th heart which would of necessity include the 2.
What about the 5 lead? There would be lower the 3 and 2 as possible 5th and maybe even 6th hearts! Then again, from 532 the 5 might be led (6 hearts then with East that didn't preempt.)
Unfortunately declarer rightly pegged West with longer hearts than East and at trick two won the A.
West showed on the following spade led then towards the K.
West was entitled to the Q and J. Two diamond tricks seemed unavoidable.

There was a winning line try on a different layout featuring an obscure small heart lead from an original K5.
NORTH
 T6
 A
 T86
 AT74
 QJ
 K
 J73
 Q963
   
 JT976
 KQ
 J52
   97
 8
 A9542
 K8

After winning the K, cash K, then A, ruff a club, A and ruff a club.
Cash A and exit a diamond to an East that must conced a trump promotion to dummy. Any of the top two of the outstanding three diamond honours with East would suffice.