Back on the bus he continued to identify wildlife for us, reversing expeditiously if any one of us thought we’d spotted something, getting angry with himself if he confused an eagle with a whistling kite at a distance of five hundred yards, and screeching to a halt whenever some racehorse goanna – the kind of tucker Ros had it in mind for me to learn to spear – went galumphing across the road.

We were now out on the Arnhem Highway, in an area known as the Marrakai Plains. It was wonderful country – spear grass and pandanus palms and water flats. I was surprised to discover in myself a strong attraction to the wet tropical landscape. Fields of daffodils had always left me dead, but a field of wild water lilies – a sudden temporary flotation of impossibly fragile colour – was an irresistible sight. A hundred magpie geese, twisting their necks like periscopes, and our first glimpse of a brolga, hesitant and retiring, uncertain whether we were worthy to watch her mythical dance, confirmed my new passion. Hereafter I was a waterfowl and wetlands man, a floodplains freak, a sucker for storks and swamps. The symbolism is too obvious even to examine. I cannot speak for anybody else, nor do I wish to plunge into the politics of whether women were ever fish, but I can no longer have any doubts in which element I originated.

We stopped for morning tea at the Bark Hut Inn, from which Tom warned us to expect little in the way of service or politeness. We ate toasted ham sandwiches and wandered out into the back gardens where there was a little wire enclosure containing a pair of scraggy emus and a disturbed male wallaroo. As Aborigines do not scruple to observe in their rock paintings, the genitalia of the whole kangaroo family can be of a prodigious size. But this chap was a prodigy among prodigies. He hobbled towards us and extended his penis. I don’t know whether he took us for dressed up wallaroos or had simply been forced by the special circumstances of his physique to disregard the niceties of species. Whatever his thinking he put on quite a show for us, fucking the fence, fucking the earth, fucking the grass, and all the while foaming at the nostrils. We weren’t too appalled. There seemed to be a specifically Australian fertility about the place. We were to return here for ten minutes on our way back to Darwin. Two dogs would be copulating outside the toilets. And in the main lounge a group of young men, awash with beer and crazed with loneliness, would be foaming at the mouth.

Before we arrived at Nourlangie Rock, to inspect the galleries repainted by the artist Najombolmi, otherwise known to Europeans as Barramundi Charlie, Tom had a few things he wanted to tell us about Aborigines.