The statue is an ornament for the garden. It is a terra cotta soldier and isn't a very big statue. Charlie Jolson describes the statue to Mark Hammond as being "the one with the stupid grin". The statue is fragile and a historical heirloom, but it also contains a kilo of smack, which is slang for heroin.
The statue was kept in the basement of the Reptilian Gallery in Hyde Park and belonged to the Triads. Charlie somehow knew of the fact that this statue was being kept in the gallery and that it would contain a kilo of heroin. He sends Mark to steal the statue and return it to him. Mark breaks into the gallery, kills some Triads and steals the statue. This angers the Triads big time, who from this point onward want Mark dead. Mark manages to return the statue to Charlie and meets him and his heavies at the Spotted Dog Pub in Whitehall. Rather than handing over the statue however, Mark requests he exchange it for Alex. Charlie however refuses, causing Mark to put the statue down on the bar, and then pointing a gun at Charlie. The pub landlord, Reggie, then knocks Mark to the floor with a beer bottle, preventing Mark from causing any more trouble for Charlie.
Although it isn't seen, it is presumed Charlie picked up the statue from the bar and returned it to his mansion in Mayfair. The statue isn't seen again, but was presumably recovered by the police at his mansion, after Charlie's death later in the day.