VC possibly Papilio memnon it looks rather like it, According to Robert Gooden a famous butterfly breeder,this is a rather varied species some having tails others not, and different colourations withinh the sex's It is also Asias largest swalowtail. Of course being in a confined area it is possible that it is hybrid form of swallowtail too
Don't believe it's a hybrid because the pupua of most species are coming from native butterfly-farms in the tropics.
I just thought they may have bred in the greenhouse/ display area you often see that here in the UK, the whole life cycle, a semi perminant self sustaining colony except in the winter months.
