When Richard Wilkinson & Kate Pickett’s highly influential The Spirit Level was published ten years ago, it inspired the soon-to-be Prime Minister David Cameron to say, “We all know, in our hearts, that as long as there is deep poverty living systematically side by side with great riches, we all remain the poorer for it.”

This expression of egalitarian sentiments reflected Cameron’s efforts to rebrand the Conservatives as a party of fairness. However, in office, Cameron’s Coalition government failed to demonstrate a commitment to greater equality: an academic analysis of tax and benefit changes during that period showed, “the bottom half lost (with the poorest groups losing most as a proportion of their incomes) and the top half gained”. As a consequence, said a report from the Institute for Fiscal Studies published this week, inequality is now so wide as to be “making a mockery of democracy".

Luckily, Cameron’s then-coalition partner, Nick Clegg, suggested a means of retaining the government’s claim to fairness. He redefined fairness. “Social mobility is what characterises a fair society” wrote Clegg, “rather than a particular level of income equality”.

Clegg retained some focus on child poverty (a problem the Blair and Brown government had substantially reduced) but gave it second-billing in the name of the Commission he set up to tackle it: the Social Mobility and Child Poverty Commission. And later, “and Child Poverty” was dropped from its name and remit.

In today’s government, the preference for using social mobility as the measure of fairness remains. Theresa May has declared an intention to make the UK “the world’s great meritocracy”.

The problem with focusing on social mobility rather than inequality is that the high social mobility and low inequality almost always go together. The UK is a good example, with both unusually-high inequality and unusually-low social mobility for a developed country. In fact, ‘Middle-Britain’ is now experiencing downward social mobility, with recent generations more likely to have a lower-status job than their parents had at the same age than they are to have a higher-status one.

I wanted to explore why the UK is now experiencing net-negative social mobility, and to understand whether it is even possible to allow individuals a fairer chance of social mobility without addressing collective issues like poverty and inequality (and if not, why not). The result is a book — The End of Aspiration? — published this week.

I wrote the book in collaboration with a group of people who have pursued ‘ideas above their station’. Some of them have a public profile (they include a billionaire, a TV presenter and two politicians) but some do not. Take my own sister, Jane. Here’s how her story begins:

The reasons why Jane was able to start school already able to read better than any other child in her class (and later to become the only one from her high school year to get into university) are explored in the book, as are the reasons why the others were able to do what they did. They gave me an insight into some of the key factors that stand in the way of people’s aspirations. Several common themes emerged.

Firstly, security. The people I interviewed typically grew up in families with low but secure incomes, and with secure housing tenures. One of the people whose story is told in the book, the MP David Lammy, says he had a “solid foundation” but that people who find themselves “moving from one bloody private rented accommodation to the next… living from one benefit cheque or pay cheque to the next, or on a zero-hours contract… that kind of poverty is a disaster for social mobility… It’s a trauma that destroys your ability to focus at school, to construct a relationship”.

Secondly, social mixing. A lot of stories featured ‘posh friends’ who revealed previously-unimagined career opportunities and/or acted as guides to the unwritten protocols of ‘elite’ careers and social circles. As with secure incomes, such mixing is now threatened: the UK is undergoing “growing social class segregation” of our neighbourhoods, social activities and schools. Once separated, different classes are offered different opportunities. For example, Joanne, an aspiring doctor, found her school didn’t teach the subjects she needed to apply for medical school, a barrier she only overcame by travelling three hours a night, four nights a week, to somewhere that did offer those courses.

Then there’s the creeping introduction of ‘toll roads on the route to opportunity’: from unpaid internships to less well-publicised issues such as the higher cost of uniforms and equipment that deter some families from seeking places at higher-performing state schools.

And lastly, the supply of the objects of aspiration. In the post-war decades, large numbers of Brits got better jobs and housing situations than their parents had had, as a result of ambitious, strategic government programmes that created such jobs (e.g. in the expanding public sector) and built homes. Since then, the supply of homes and good jobs has not kept up with demand, and Brexit won’t improve our ability to negotiate trade deals in which the UK specialises in high-value industries with high-quality jobs: people who are known to be desperate for a deal rarely get a good deal.

Insecurity and social segregation are linked to inequality in obvious ways, but so are the ‘toll roads on the route to opportunity’. People in influential positions are usually affluent enough not to be bothered by them, so there is a lack of pressure to keep these costs down. And inequality also affects the limited supply of homes and good jobs (when inequality is high, the privileged are more able to out-bid the rest of us for scarce opportunities).

I’m not arguing that inequality and collective wellbeing are important and individual opportunity is not. I don’t see why the aspirations of individuals should be put on hold until everyone’s aspirations can be met. As someone put it to me, “middle-class people expect working-class people to wait – for socialism or whatever – why should we wait?”. I do think that encouraging individuals from the ‘lower classes’ to join the ‘establishment’ is necessary if the establishment is to understand how to raise the collective wellbeing of everyone else (ladders are best designed by people who know what it’s like to climb one). What I am saying is that — as the quantitative data suggests — neither individual opportunity nor collective wellbeing can be achieved alone. Like any good team, we achieve our individual goals by working together.

The End of Aspiration? Social mobility and our children’s fading prospects was published by Policy Press on 15th May