REBECCA ROOD'S MAILBAG..........
Dear Rebecca,
During a recent intercity league match my partner and I bid our way to 6D, having unearthed a massive 6-5 fit in trumps,  alongside plenty of controls in the side suits.
When dummy came down I had only one side suit loser, missing the Ace of Clubs.  However, the slam required me to pick up the King of diamonds.
Quickly in with the Ace of hearts I played the queen of diamonds from hand towards dummy's Ace, hoping to pick up an inadvertant tell from either of my two opponents. No such luck. My LHO quietly played in tempo the deuce. Decision time : do I go up with the Ace or finesse ? I finally opted to play the Ace only to see ( shock, horror ) my RHO show out.
With other pairs comfortably bringing home 5D,  this was a game swing against us. 
What would you have done ?

Yours Des Perrin
......
Dear Des,
Your letter reads like a sad story where given a 50-50 chance you just happened to guess wrong. Yet in my opinion you didn't go with the true odds.
With two cards missing there are just 4 layout  scenarios : 
K2.......void
K .........2
2...........K
void......K2
And if you were told before playing a card your LHO did not have a void ( which proved true ), then there are 3 scenarios left,  two of which involve your LHO holding the king. This represents odds of around 67%.
So when your LHO dropped the deuce,  you can either take the view that the original odds still apply, or that there are only two scenarios left to consider, where the revised odds move to a straight 50-50 guess on who has the King.
Then of course there is the theory that if there are wild suit distributions all round, this suggests that a 2-0 break in diamonds is more likely than a 1-1 split. Therefore if your LHO shows up with the deuce, he has also got the king.
So I would have gone for the finesse,  because I believe my way of thinking gives me far more hope and optimism than the harsh realities of statistical probability. 

Yours never one for maths at school, Rebecca