Even experienced political commentators waste time analysing and explaining the careful strategy behind senior politicians’ big decisions, when often no such a strategy exists.

In reality, everything about life in government departments pressures politicians to behave in ways that are reactive and short-termist.

Richard T. Kelly’s new political thriller The Knives – which follows a fictional Tory home secretary through a blizzard of political and personal traumas – explains this better than anyone in recent times. It often takes such creative works of fiction to help visualise what life is really like.

I was director of communications at the Department for Education between 2011 and 2012, during two of the most gruelling years for education reform. Working closely with secretary of state Michael Gove and his advisers – as well as the senior communications team at No 10 – it was a fascinating window into how politics works.

There are four big things Kelly gets right in his description of life as a secretary of state. The first and most important is that politicians make many decisions on the basis of competing pressures. Michael Gove and his team were highly principled – far more than most – and they wouldn’t give an inch on some matters.  But not even the most ideological revolutionaries can fight every battle. Progress on the most important issues sometimes means compromise on others.

Politicians may decide they can’t take a particular policy route because of the popular backlash it’ll cause or the political controversy it’ll stir up. Sometimes No 10 or The Treasury tell departments that they can’t do something for similar reasons. If one part of the machinery of Government gets spooked about something – and this happens a lot – then everything can grind to a halt.

Those that exert public pressure – directly or through the media – therefore have a much greater chance of being listened to, because politicians often just need to avoid rows to keep the show on the road. Those organisations that spend large sums on traditional public affairs are completely wasting their money. For the most part in government, those that quietly explain their case are ignored, while those that take battle to politicians stand a chance of changing things.

The second big thing is that secretaries of state aren’t in control of their Departments to any meaningful extent. While they can bring in two or three special advisers, they control few other personnel decisions. Consequently, some of the most important policy areas can be managed by officials that are either incompetent or ambivalent towards the policy in question.

In Kelly’s book, the home secretary ends up losing his temper regularly with his staff. I never once saw Gove do that, but he would have been well within his rights to have done so at times. With no ability to hire and fire, even the biggest mistakes can go unpunished. Shouting often seems like the only thing secretaries of state actually can do.

The third thing Kelly nails is the sheer number of enemies that secretaries of state have – both internally and externally. Whether it be obsessive journalists with a personal axe to grind, hostile colleagues or opposing politicians and activists, secretaries of state are big targets. As such, and along with the endless risk of internal mistakes, there is a lot of flak to contend with. Much of this can’t be anticipated and comes at short notice and demands an immediate response.

The fourth thing is that senior politicians aren’t in control of their time at all. As Kelly shows, the secretary of state’s day – often until late at night – is filled with meetings that they cannot but attend. Cabinet meetings take up time, Parliamentary demands (particular with John Bercow as speaker) take up even more time and then there are requirements to do extensive work for the Party, especially as elections near. When Kelly’s David Blaylock stumbles from unwanted meeting to unwanted meeting, this perfectly mirrors reality.

Kelly never shows Blaylock in long policy or communications discussions with his team. That’s because – while not unheard of – they happen rarely. In government departments, the clocks run faster than ordinary ones and endless decisions are required - with little opportunity for discussion - all the time.

In many ways, it is surprising that more mistakes don’t get made.