In 2015, David Cameron became the first Conservative leader in 22 years to win a parliamentary majority and thus far the only Tory leader to win a parliamentary majority in the 21st Century. While the size of the majority at Westminster was small, the scale of the triumph in individual seats was enough to make it all but certain that the Conservatives would remain in power not only for the length of the 2015 parliament but following the next election as well.

Symbolising the triumph was the Tory forward march among ethnic minority voters: the Conservative Party polled a million ethnic minority votes, according to a much-hyped Survation poll shortly after the election result.

Then there followed an election in which Theresa May lost that majority following a political playbook based around consciously abandoning the political approach preferred by David Cameron. The Conservative pain point appeared to be in two groups: social liberals and affluent ethnic minorities. If the Tories had done as well in the 100 most diverse seats as it did in 2015, then May would have retained her majority, albeit a still-smaller-one than that enjoyed by Cameron.

Thanks to a new study and analysis for the Runnymede Trust by Manchester University’s Nicole Martin, we now know that essentially everything we thought we knew about the 2015 election, the Conservative Party and ethnic minorities is wrong: there was no breakthrough in 2015, although the Conservatives did make small but significant gains from 2005 to 2010 among ethnic minority voters.

In addition, the political pattern in the 2017 election turns out to be more complicated than we thought. The pattern in 2017 was of the Conservative Party falling back with British voters of Pakistani and Bangladeshi descent, but from a lower base than previously expected. Among British voters of African descent, the party trod water.

The Conservative Party did significantly better with British Hindus in 2017 than in 2010 or 2015, going up from 30 per cent of the vote in 2010 to 40 per cent in 2017. Among British Jews, according to the University of Manchester’s long-running survey of voting behaviour by voting groups, the Conservative Party did significantly better in 2017, going from a dead heat between Labour and the Conservatives in 2010, with 63 per cent of British Jews voting Conservative and just 26 per cent backing the Labour Party.

All of which, added together, means that our understanding of what went right for the Conservative Party in 2015 and wrong in 2017 requires something of a rethink. The question of how the Conservative Party does among minorities is going to become more acute in future as the British electorate becomes more diverse and the minority electorate becomes more diffuse. Before the 1987 election – the last election to produce an enduring Conservative majority – there were no seats in which more than 30 per cent of the population was from an ethnic minority. There are now 110.

In 2017, the Conservative Party was able to retain office thanks to an infusion of older white voters without degrees who largely backed a Leave vote, but there are two reasons why this coalition doesn’t look futureproof. The first is that, bluntly, the proportion of older white voters without degrees is set to decline through mortality and demographic change, and more worryingly is not well-optimised to win power under first past the post. The second is that it is hard to see how the Conservative Party can continue to win majorities on the back of Leave voters when the expectations voters have of Brexit are both high and varied. The Tory party’s 2017 coalition is now disproportionately vulnerable to a Ukip revival in a way it wasn’t under Cameron.

So what does this new information tell us about the Conservative Party’s present and future?

The significant lesson is that Cameron’s big electoral success wasn’t among well-paid ethnic minorities but among their white neighbours. This is revealing of a broader part of the importance of David Cameron’s political project: it’s not just that in a more diverse democracy, you need to get ethnic minorities to vote for you – in a diverse, fairly well-integrated democracy like the United Kingdom, increasingly it will be a bar that has to be passed among white voters, too.

The bad news is that having thrown that into reverse, and with the position among ethnic minority voters worse than we thought, that challenge looks a lot bigger than advertised.

What about the two minority groups that May did better with than Cameron? Well, that’s more of a mixed picture. The Conservative Party can take no useful lessons from its improved position with British Jews from 2015 to 2017 as it is, visibly and obviously, something that has very little to do with a positive offer from the Tory party and everything to do with the changing relationship between the Jewish community and the Labour Party. There are no useful positive lessons to be taken from the improved electoral performance of May over Cameron.

There is however a useful negative lesson, which is that it doesn’t matter how well-aligned you are on other issues, if you are not trusted to look out for the interests of a minority group, that group won’t vote for you. The one good news story for the Conservative Party lies in the British Indian community, which in many ways is behaving in exactly the way a Tory strategist would hope – as British Indians become more affluent they become more inclined to vote Conservative, and that pattern is stronger still among specifically Hindu voters.

But there’s a sting in the tail here: in the movement away among British voters of Bangladeshi and Pakistani descent, particularly Muslim ones, from 2015 to 2017. Again, as with the movement away from the Labour Party among British Jews, you don’t need to be Hercule Poirot to work out what has happened here: a political party that has licensed Islamophobic campaign techniques in the country’s capital and been sluggish at best to expel activists and councillors sharing Islamophobic content is not going to win support from British Muslims, even if they become more affluent.

And that’s perhaps the most important lesson here: that the Conservative position among ethnic minorities is worse than we thought and that a great deal of work, both in terms of increasing affluence and reducing the reasons why ethnic minority voters distrust the Conservative Party, is required.