NORTH
 KQJ94
 KQ4
 KJ73
 3
 A2
 8532
 QT86
 642
  T8
 A97
 A9542
 KJ8
  7653
 JT6
 
 AQT975
Dealer: East    Vul: EW   MP Scoring

West

Pass
X
Pass
Pass

North

3
4
5
Pass

East
1
Pass
Pass
Pass
Pass

South
3
4
5
5

Unilateral Departure from Partnership Agreements 

South thought to take advantage of East's diamond announcement by preempting with only 1 fewer club than 3 promises, and with an outside 4 card major.
"Two, two, two breaches in one."

North's 9 was enticement enough to bid a forcing 3 and South was left with some bad options: A hand so good in support of spades that North could not possibly be expected to guide the partnership to a proper contract.
Once again, South would have to take a unilateral action.
"Oh what wicked webs we weave when first we practice to deceive."
But...but...it was the opponents who were supposed to be deceived...THE OPPONENTS!

What kind of 3 preempts over 1 include 4 spades?
None.
But...but...but...the vulnerability was right, not vulnerable against vulnerable!

How do you value the South hand in support of a forcing 3 spade bid?

What is your idea of a suitable hand for a 3 spade bid opposite a hand that possibly include no more than seven clubs and the J?
Don't you need something like 20 plus points to be making forcing bids like that?

Opposite 20 points, holding 6 points in clubs, 1 point in hearts and 5 points for the diamond void, the opponents TWICE announcement/bragged of suit, the opening bid and the double, don't you think that there's a good chance of a slam? Isn't the South hand worth at least 12? Nothing for the side suit of 6 card length, including the T9?

South was "between a rock and a hard place".
North's 4 bid should have been a discouragement for South and suggested perhaps a 19 point hand.
South was hoping North would pass the 4 double to enable a stronger showing of a limited 3 preempt.

South decided that no discouragement was sufficient enough, given the required range of a forcing 3 bid, and decided for some reason not to jump to 6, perhaps because the 5 cuebid showed the preemptive 3 bid of 3 bids. After all, bidding 5 wasn't as final as passing 5, right?

Still hope? Still hope?