I've been saying for a long time...
That Khan needs some bloody defense.
The very first thing I noticed in round 1 - Where was the head movement?
Khan's neck was as stiffly upright as a tree trunk. Combine this with the fact that he has a VERY bad habit of dropping his guard during/just after punching, and you can see that it's no surprise that he was knocked down. Limond also (smartly) exploited this leaky defense by sitting back and fighting in the mode of a counter-puncher, trying to catch Khan coming IN, so that the momentum added to the overall power of the blow, and his plan worked perfectly right up until Khan threw a spanner in the works - he showed that he has heart. He got back up, even though his legs looked like they had gone to jelly, and he broke Limond's jaw and nose, bloodied his face and basically shifted into his top gear, hence why Limond's corner quit. I'm surprised that people like Amsterdam are jumping around shouting about the chin issue - yes, it does confirm that Khan has a shaky chin, but is no one impressed by the grit he showed? He dug deep and showed a warrior mentality. That's something that our other olympic medallist, Audley Harrison, has continually failed to do, again and again.
Big congrats to Limond on putting up a hell of a fight. Great fighter.