Perhaps it was because our guide&rsquos name was Friday and it was a Friday that we had such luck. That&rsquos certainly what the children thought. It was our second day in South Luangwa National Park &mdash a vast protected wilder­ness the size of a small country in the east of Zambia &mdash and we had been bundled into an open jeep at first light. As we crossed the sprawling Luangwa river we saw a family of elephants swimming home to the park after a night of foraging in nearby villages, and two fishermen in their small boat glide across the brown and silver water, undeterred by the river&rsquos large crocodile population.