I believe the consensus was that he was approximately 170cm (5'7") which was, contemporaneously, fairly average. There is a surprisingly large number of Google hits relating to why he was perceived to be short but none that offers a definitive answer. The most compelling is that he was constantly surrounded by large bodyguards which gave the public the impression that he was not tall.
What I had understood was that it was due to the fact that the French foot was larger, so he was 5'2" in French feet which sounds short to someone used to the English foot. I honestly have no idea what the truth is.
