Ten people who changed the world: Tom Watson, MP who shook the world of British politics

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Tom Watson is one of those who has changed forever the media and political culture in the UK (Steve Schofield)

Most MPs wield no power and little influence. The sense of powerlessness is especially intense for backbenchers that languish in opposition soon after their party is ejected from power. As a Labour MP in this current Parliament, Tom Watson was in such a position.

There is only one way for such peripheral politicians to make an impact. They can focus on a single issue over which they feel strongly and refuse to be diverted from their chosen cause. This is what Watson did and as a result has had more impact on public life than most ministers.

Watson's activities did not bring the hacking saga to its first breathtaking climactic – the revelation that the phone of the murdered teenager, Milly Dowler, had been hacked was the spark that lit the fire. But Watson had displayed dogged, courageous and forensic resolution before the blaze erupted and continued to do so as a powerful elite sought to cool the intense heat.

His focus before the news about Dowler's phone was pivotal. It is easy to forget how unfashionable the pursuit of the hacking saga had become. The Labour leadership was not interested and Ed Miliband's media adviser, Tom Baldwin, had written a memo to the shadow cabinet urging them to keep clear of the subject. In what now seems a distant land, the priority of Miliband was to woo News International and not to challenge the mighty empire. Most newspapers had lost interest, in some cases for obvious reasons. This is the phase when a less determined MP might have lost interest in a cause.

Watson kept going. In doing so he had two advantages. He knew he was right and that a scandal of mind-boggling proportions was being casually or determinedly unexplored. It always helps when there is no room for doubt as an MP sticks to his unswerving course. The other helpful factor was that at some point he knew vindication would come. There was too much evidence for the scandal to remain buried forever. None the less, with the party leaderships, the police and much of the media turning away, Watson made his distinct mark. Most specifically, he used Parliament to full effect.

This is highly unusual. A lot of MPs are used by Parliament in the sense that they are no more than lobby fodder for their respective leaderships. To use Parliament as a stage on which to advance an unfashionable crusade is a neat reversal of orthodoxy. At Prime Minister's Questions, whenever Watson was called, a silence descended from nowhere as if the rest of the Chamber sensed that he was on to something but did not really want to know. His early target was Cameron's former press secretary and News of the World editor, Andy Coulson. In retrospect, Coulson's departure from Number 10 at the start of the year was a sign of what was to follow. But Watson aimed much wider in subsequent questions, articles and in his role on the Culture Committee, an institution that has acquired greater significance partly as a result of Watson's persistence. The rise in the prominence and importance of parliamentary committees is one welcome consequence of the drama.

Watson's determined hyperactivity meant that when the grim reports about Milly Dowler's phone surfaced dramatically in the summer, he and a few other MPs were ready to strike. His readiness was an absolutely central part of the saga. Without the likes of Watson, a shocked public would have turned its fire on Parliament as well as parts of the media. It would have posed a damning question: why had the entire political world turned away? Instead, the political world had a voice and one that knew more or less every twist of the tale. Suddenly, Messrs Cameron, Miliband and the rest could hide behind Watson and agree that he spoke for them all.

His subsequent questioning of suddenly humbled key witnesses brought before the Culture Committee helped to cast more light on what had happened. In itself the symbolism was vivid. Watson and others were the masters now, as the Murdochs and their senior entourage apologised for what had happened, a reversal of roles that many of the most supposedly powerful political leaders never expected to see in their lifetimes – the elected politician making life uncomfortable for mighty media executives. More important, Watson was forensic in his questioning, especially in relation to what key figures knew and when.

Watson was by no means alone in sticking to his course, but as a Labour MP on the opposition benches he was less well placed than some to make an impact. He made the most of what he had on his side, the truth and a parliamentary platform. In doing so he is one of those who has changed forever the media and political culture in the UK.