Firstly, I'm not convinced that there wasn't a change of course by L; albeit that the helmsperson may not have induced it.
My (assumed) findings subject to a clearer answer to the above : 
L (ROW) lost control of her mainsheet and suddenly altered course and heeled quickly to windward. There was contact between the mast tops of W and L that caused damage. W failed to keep clear of L. L failed to avoid contact with W.
My conclusion : 
W was keeping clear of L until L lost control of her mainsheet. In not keeping clear of L, W broke RRS 11 and 14. 
L failed to avoid contact with W and broke RRS 14 (and probably 16.1).
My decision : 
The contact with W was caused through no fault of her own (not having time to avoid the contact, albeit not ROW boat, thus need to find on 16.1) and L broke a rule of Part 2.
W is exonerated (RDG) for breaking RRS 14 (and probably 11).
L is DSQ for breaking RRS 14 and possibly 16.1 as well.

Let the debate begin.

There is a third alternative. 14 states "If reasonably possible". It would appear that it was not reasonably possible for W to avoid contact, so no breach of 14 by W. Whether or not it was reasonably possible for L to avoid contact would depend on why the heel (with no change of course) took place. If the PC found that it was not reasonably possible for L to avoid contact, then W would be in breach of 11 and there does not appear to be any basis for 43.1(c) to apply to W.

If W was unable to avoid contact: if L immediately heeling to windward caused the contact then can L be penalized? Then again how is W unable to avoid contact? W could have changed course to windward. Since W is not the ROW boat there should be someone watching L's moves. Avoiding contact is the most important act a skipper can take other than avoiding human injury.

Ah ! That is the trap Chin. If it was not reasonably possible for L to avoid contact with W, nor cause contact between them, then L would not have broken 14, so 43 does not apply at all. Very unfair in these apparent circs, but who ever said RRS were fair ?

Simples - W was not keeping clear….

I think Matt is correct.  It's unlikely that L changed course, especially to windward, given the heel and associated weather helm.
This may be one of those unfortunate situations for W that isn't covered by the rules.  W was obviously quite close to L.  Maybe less than a boatlength to allow this to occur.  

W kept clear by definition. 
L did not change course. 
W exonerated of contact. 
L should have taken a turns penalty. 
Who hailed Protest?
Who would dare take the 50-50 shot in the room and file?
L should offer over beers to pay for repairs. 

Phil-  Please 'splain how W kept clear 'by definition'.  And when you write the conclusion in the hearing, under what rule would you penalize L?  I read the definition of keep clear, and I don't think W kept clear.  L was indeed sailing her course, but while doing so, she inadvertently dropped her mainsheet (I know about that!)  At that point she would have had to take avoiding action to prevent contact with W, so by the definition it seems to me that W was not keeping clear.  I think 'tough luck' for W.  And this likely happened in about a second, and L did not break 14.