I was told when i purchased my Royal that it was a female, however from what i've seen in python books and online research, it seems to be that my python is a male due to the size of the tail. Is there any other way of telling whether it is male or female apart from probing?
Not really, no. There are some visible differences such as the tail and the size of the anal spurs, but as they vary from animal to animal even an expert with two royals to compare between couldn't say for definite.
The best way to know is to have him / her probed by a vet, but even that isn't 100% as a male can probe as a female if he tenses up. Babies can be "popped" but again this needs to be done by either a vet or an experienced herpetologist, and it's only suitable for very young snakes.