From an earlier sighting (4635368) I learnt this spider was called a Jumping Salticid Ant Eater (Zenodorus orbiculatus). I found this one as I was taking photos of a Jumping Jack Ant nest I’d just found. The last 4 photos depict the sequence of its encounter with a, (very aggressively pumped up), Jumping Jack Ant (upper LHS). I suspect neither of them wanted to follow through! (Apart from the spider being distracted by another type of ant).
(The Jumping Jack is bigger and has a potent sting, I know, I’ve been stung often enough. However I don’t know what this spider brings to such negotiations, so that is my next question to pursue.)