What did the elephant symbolise

The elephant itself could be said to symbolize the colonial population of Burma. Even though the elephant is in his own natural habitat, he is restricted in his movements, as indeed are the local people. This is their country, their land, and yet it doesn't belong to them anymore; it is controlled by their colonial overlords. When Orwell is faced with the elephant, his conscience tells him that it's wrong to kill the animal; it is a fundamentally harmless animal driven mad by an extended period of captivity.
For Orwell, as a colonial military policeman who has come to loathe imperialism, there's a clear parallel between the elephant and the Burmese. But in both cases, he has no choice in the matter. He's a military policeman, and, like all colonial employees, he needs to do his duty and uphold the law in front of the indigenous population. Otherwise, the authority of the British will be undermined. He accepts that the elephant has been mistreated, as indeed have the Burmese, but he must put all moral qualms aside and do what's expected of him. He doesn't want to control the elephant any more than he wants to be a party to controlling the Burmese, yet he must. The law, however unjust, must prevail, and the shooting of the elephant represents the triumph of law over conscience.