Poland?
(Well, aside from the vast territory thing).
Anyhoo, political Islam was barely a little sprout at the time [1], so I'm not sure why they would have
much more trouble than in Central Asia...unless the British stir up trouble, which they almost certainly would.
Bruce
[1] British Egypt? There was a _lot_ of the Islamic world being ruled over by Europeans at the time - it took a while for the reaction to really set in. Russia is unlikely to hold onto Iran in the long run, but if they can come to some sort of gentleman's agreement with the British, I don't see why they couldn't hold onto it for a few decades without excessive strain on the Empire as a whole.