The March is set in an unspecified near-future, when climate change has started to make parts of Africa uninhabitable and the continent remains wracked by war and chaos. Fed up of being in a situation not of their making, a charismatic Sudanese leader encourages a mass exodus of refugees to cross the Mediterranean and seek refuge in Europe, where they can make a better life for themselves. The reaction from Europe and Britain in particular - as the bulk of the refugees seek to land at the British outpost of Gibraltar - is one of panic and a divided political response, with the urge to do humanitarian good brought into conflict with concerns over practicalities and outright prejudice.
The drama has not aged tremendously well, but some of the issues it touches on are, 25 years on, startlingly prescient. The biggest mistake is does make is massively underestimate the scale of such an exodus, with "only" 250,000 refugees on the move in the film. It's also rather simplistic: the refugees cross the sea in a single mob at a single location and are easily turned back by the forces of Europe. The notion of multiple hundreds of thousands of refugees trying to cross into Europe by both land and sea from multiple directions simultaneously is clearly one the TV writers had not considered.
Still, it is interesting to see that a quarter of a century ago people were aware of the dangers that constant war and chaos in other parts of the globe would encourage flight on a massive scale to safer areas of the world, even if they could offer no constructive solutions on how to deal with such a situation.