The Jatbula Trail is one of the Australia's most scenic short walks (its only 58km and takes 5 days). Walkers are only allowed to camp at the official campsites (which also happen to be the most beautiful spots). Bookings are essential as only 10 walkers are allowed to start the walk each day (all walkers must start from Katherine Gorge). We booked 6 months in advance and got the last two places in the week we wanted to start (and it wasn't the school holidays either). It is a very popular walk so I would book as early as possible. I'd advse you to call the ranger station at Katherine and see if there are any openings left this season. The rangers are very much on the ball with permits and will check them on the trail. The boat company (which gets you across the Katherine River) also know there is a limit of ten walkers per day and if the numbers didn't add up I would suspect they would pull you up. You may be lucky if you just fronted up for a permit (maybe somebody will cancel at the last minute) but I wouldn't rely on it. Good luck, it's a great trail.