Bakes is on the money for sure. Black Whips are very common in the Top End. If you corner them and they get mad, a white fleck becomes visible under the raised edge of each scale, giving them a speckled appearance. They are bloody fast when cranky, so by that stage you should be backing off!

Here's a pinched photo, they can be any colour from olive or light brown through to jet black. Black ones are common around Darwin.