Most images of migrating wildebeest are hackneyed and offer little to excite. The river crossings during the summer months have been endlessly documented by scores of tourists who gather along the riverbanks with their telephoto lenses and shoot away on their motor drives from the first leap to the last. There is no serenity in the content here and no originality in its photographic execution.

In my mind, the scores of crossing images in stock libraries have two specific aesthetic drawbacks: firstly they tend to be taken when the sun is quite high – never the best lighting conditions and secondly, the chaos that unfolds in the crossing can make the wildebeest appear ungainly, generic and rather marginal. They are not animals that tend to elicit huge emotion and I think part of the reason for this, is that they are so often photographed at these well established river crossings where their behaviour suggests fear rather than freedom.

One late afternoon in Amboseli it became increasingly clear that a tremendous storm was building up above the lower slopes of the Kenyan side of Kilimanjaro. This is not that unusual and on many occasions I have worked with dark clouds in the afternoon of the dry lake. On this day, however, the sky had an almost biblical menace with its haunting deep blacks full of foreboding. The heavy rain was localised and painted downward waves in the sky – almost akin to a flock of starlings.

I was conscious of the fact that the animal behaviour on the flat and elemental canvas of Amboseli appeared more skittish than normal and around 5.30pm I started to photograph panicked zebra herds charging off in all directions.

But images such as the image above, misrepresent the spectacle of what was unfolding in the sky above, because on this occasion I was working with the late evening light that was bursting out from time to time, rather than against it. The big sky needed to be the picture, not excused from the picture. There was only about 20 minutes of light left and I needed to capture the mood of what appeared to be an impending apocalypse.

The best plan was to leave the protection of the vehicle and lie flat on the ground shooting directly into any shafts of evening light. Of course, I needed foreground context as well as the sky – but this was largely in the hands of fate. The image above has a great deal going for it – in particular, the lone zebra having a good old roll around in the foreground. There is a palpable sense of place to this photograph.

However I was searching for a more dynamic spectacle and a vignette with greater movement – in particular I wanted two storms to coalesce – the storm in the sky and a potential storm in the sand. This needed the help of the wildebeest that were increasingly spooked by the thunderclaps and I needed them between myself and the horizon. My regular Amboseli guide – Juma Wanyama – was able to use our four wheel drive as a decoy and softly coerce the herd in the right general direction.

Exodus achieved my goal and more – it was the last picture I took that day and minutes later the light had gone. As I picked myself up from the ground and reunited with Juma, I had no preconception of how much information was in the sky, but the new Nikon D810 is a high performance camera body and will pick up more than my naked eye. The dead tree to the right adds to the Mad Max mood of the image and there is really nothing in Exodus that I would want to change – even the blurred blades of grass that hint at my position flat on the dustpan add to the mood of the image.

What is also special is that the wildebeest – unlike at river crossings – look independent, gamely and free. There is great serenity and soul to this picture – which is surprising, given that at first glance it could appear to offer a darker message. Exodus is Africa at its incomparably evocative.