It will definitely be worth watching.
But I don't think this claim in setting up the opening film was quite accurate - though it is very common, even from leading 'broadsheet' media outlets and from leading politicians too.
Mason reported that:
Its about the decline of social mobility in the absence of a viable economic model and a deep unease about where we stand in a globalised world. I am going to travel from the eastern tip of Britain to the west in search of answers.
The fact is, in the the last 20 years, social mobility in the UK has declined.
And now, for the first time since the '30s, a generation will grow up poorer than their parents.
The problem is locating the decline of social mobility as something that has happened in the last 20 years, between 1990 and 2010.
The sharp collapse in British social mobility (observed between the 1958 and 1970 cohorts) took place in the late '70s and the '80s.
Let us return to Next Left's social mobility fact check service, which rounds up the key academic references and links.
The authoritative LSE studies reports on more recent trends that:
We cannot find any evidence that the sharp drop in mobility observed for children growing up in the 1970s and 1980s has continued. But nor can we find evidence that mobility has improved.'
This was based on using proxy measures to look for mobility changes for children born around 1985 (the average age for the children of the '58 cohort) and 1999 (for the children of the 1970s cohort).
It found that "the decline in intergenerational mobility that occurred between 1958 and 1970 birth cohorts is unlikely to continue for cohorts born from 1970 to 2000" - but that there was no significant recovery in mobility either.
So social mobility did decline (and sharply) 30 years ago.
In the last 15-20, it would be more accurate to say that it has stabilised.
It is not a technical difference. It matters, because we would otherwise risk as writing off policies as having failed in reversing inter-generational disadvantages, when they have barely yet been given a chance. In fact, some of the early evidence - as recounted in Jane Waldfogel's recent Britain's War on Poverty - is that the policies have begun to provide an important foundation for success in this long-term challenge of breaking down inter-generational disadvantage.