Earliest post-1800 partition and defeat of the Ottoman Empire

Suppose that there's an event that occurs, whatever it might be, that leads to the Western powers no longer saving the Ottoman Empire. What's the earliest possible post-1800 event that would lead to this? What would the partition look like?
 
Seems to me that the only way for that to work out would be for Russia to not be the main beneficiary of a partition. Otherwise, Britain puts its foot down.

Actually, one other alternative would be analogous to the OTL WWI, with Britain elevating a Russian alliance over who controls the Dardanelles. In which case they'd be game to participate in the dismantling. I'm not sure how you'd get that without a durable French-German alliance, though.
 
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