The arrival of the new royal baby reminds us that not only are mixed-race people the UK’s fastest-growing ethnic group; it also underlines that what it means to be mixed race is changing. Archie Harrison Mountbatten-Windsor will join the ranks of those second-generation mixed-race people who challenge our very perceptions of ethnicity and black identity.

In fact, the changing face of mixed-race Britain is something we barely notice even as we are looking directly at it. Perhaps that is the point. Back in the early 2000s we were vaguely aware that young celebrities, such as the late reality TV star Jade Goody or footballer Ryan Giggs, had a black grandparent. But they rarely discussed it or talked of how they perceived themselves.

Most of us watch the actor Stephen Graham, or cheer footballers Ross Barkley and Kieran Trippier without registering their ethnicity. Did you just presume they were white? Before you congratulate yourself by saying, “I don’t think about race. It doesn’t matter to me”, it is not that simple: maybe it matters to them. Their connection to a black identity, and whether others recognise it, might be something they feel is important.

Our current view of mixed-race Britain, particularly in the context of the black (African/Caribbean) community, has become so familiar that it is now almost a cliche. I know it because I have lived it. When I was growing up in the 1970s and 80s, with a Jamaican mother and white English father, being mixed-race was not always easy, but it was relatively simple.

“White” was an exclusive club to which someone like me did not belong. I was more likely to hear “half-caste” on the school playground than “nigger”, and occasionally it was other black people, as well as white people, who made me feel like an outsider. But there seemed little doubt that society viewed me as black. I also learned I was black through positive experiences and a sense of belonging. In my mother’s family, as with most Caribbeans, we go from dark skin and tight afro-hair to lighter skin and soft curls, with every variation in between. Whatever “black” was, I knew it was broad enough to include someone like me. I embraced it. It was not only how the world saw me, but how I wanted to be seen.

Facebook Twitter Pinterest Chelsea footballer Ross Barkley has a Nigerian grandfather and could have played for Nigeria but chose to represent England. Photograph: John Sibley/Action Images via Reuters

But alongside that “first-generation” experience of being black and mixed race, there is a new story that we have barely begun to discuss. What if my connection to my black heritage was not through a parent, but through a grandparent or great-grandparent? What if my physical appearance had not been different from my white classmates? Would I have experienced racism? Would I have felt included in being “black”? Would I have wanted to be? Should I have wanted to be?

Thousands of young people across the country are now grappling with those questions every day and their numbers are growing. The random shuffle of genes means that some will experience life in the same way as their mixed-race parent. Others will not, their African heritage revealed perhaps by their dark eyes or the curve of their nose, visible only to those who are looking. It is a feature of black heritage, ethnicity and identity we rarely hear about and it prompts wider questions: what will it mean to be mixed race or black in the UK in 2030, or 2050?

Of course, black people in the UK have a long history of integrating and intermarrying into wider society. Furthermore, mixed-race people span all ethnic groups, not just those with black and white parents. But it is important to recognise that this phenomenon has a particular new significance to black Britain, for two key reasons.

First, interracial relationships and the growing mixed-race population is something the British black community is experiencing in exceptionally higher numbers compared with other groups. According to the 2011 census, members of the black community are among the most likely to choose a white partner – close to 50% for black Caribbeans. (In contrast, those with heritage from the Indian subcontinent generally have a rate of interracial relationships that is much lower.) This likelihood also increases with each new generation: the chances of people of mixed black/white heritage having a white partner, are about 80%. The demographic implications of this for the future of black Caribbeans in Britain are obvious.

Dr Adam Elliott-Cooper, a research associate at the Department of Geography, King’s College London, who is himself mixed-race, puts it succinctly: “In the absence of significant new immigration, British Caribbean people, as we know them, are going to become largely absorbed into the wider white British community within a few generations. For the most part, their great-great-grandchildren are going to look very different from them.”

Trying to understand this phenomenon by drawing on the US black experience does not help, because this high rate of black interracial marriage is a very British phenomenon. African Americans in the US are among the least likely to have a partner outside their own ethnic group.

Second, although the integration of black people into a majority white community has happened before, it was in more brutal times. The idea of a “one drop rule”, which meant that even those with distant African roots were “unpure” and would be treated as black, now seems farcical. Similarly, the days when many mixed-race people tried to “pass” for white and lived in fear of their “dark secret” being discovered feels ugly and archaic. That history provides little precedent for today’s young people, who are unlikely to hide their heritage or define themselves based solely on race. If they are inclined to discuss the complexity of their heritage at all, it will be on their terms.

Facebook Twitter Pinterest The actor Stephen Graham’s mixed-race heritage – he had Jamaican and Swedish grandparents – has played a strong part in his life. Photograph: David Levene/The Guardian

In this regard, the Liverpudlian actor Stephen Graham may be a trailblazer. It is beautifully ironic that the mixed-race grandson of a black Jamaican immigrant rose to fame playing a white, racist, skinhead in Shane Meadows’s 2007 film, This is England. Graham talks comfortably about his pride in his grandfather’s heritage and how it has shaped his identity. He also describes how he has challenged white racism when those around him thought they were safe to express unpleasant views about black people in front of him. The nuances and complexity of how someone such as Graham sees his black heritage in 21st-century Britain may now seem exceptional. They may soon be commonplace.

A new understanding of what it is to be mixed-race in the UK means listening to voices that have often been missing. We frequently hear white liberals discussing interracial relationships in effusive terms, as if such relationships are, of themselves, the living embodiment of a happily integrated society. But it is worth remembering they do so in the context of less than 5% of white people being in interracial relationships.

We rarely hear from the black perspective. Even for those who feel overwhelmingly positive, a growing current of existential concern exists. For some black people, the increasing dominance of interracial relationships can feel like a devaluing of relationships between two black people. More pointedly, in a society where the stereotypical appearance of mixed-race people, with light brown skin and curly hair, is held up as the perfect symbol of Britain’s exciting multicultural future, how does that make you feel if you are a dark-skinned black person with afro hair?

A black perspective in these discussions is so important. The country has been fascinated by how it might feel to have the Queen’s great-grandson recognised for his African-American heritage. Few have stopped to think about how the Duchess of Sussex, or her mother, Doria Ragland, would feel if he were not.

Perhaps the least discussed aspect of second-generation mixed-race Britons is how it feels to be their mixed-race parent. In 2015, Miri Song and Caitlin O’Neill Gutierrez of the University of Kent, published a groundbreaking paper entitled “Keeping the story alive: Is ethnic and racial dilution inevitable for multiracial people and their children?”. It focused on 64 parents, most of whom were first-generation mixed-race people with a white partner, and discussed how they felt about the ethnic identity of their children. The findings were not what I expected.

Four key themes emerged in the study: the loss in their children of “cultural knowledge” connected to their parents’ ancestry; the “embodiment of ‘white-appearing children’ and the effect of physical markers of minority heritage not being present in their children”; a notion of “reduced racial fractions”; and concerns, among partially black participants in particular, about “whitening” and the loss of politicised racial consciousness.

I think what really bothers me is I don't want my children to forget that race matters. It affects people's life chances. 'James', a mixed-race father

When I first read this, I was stunned. The participants seemed to be echoing some of the most unpleasant views I had heard as a child. “Racial fractions”? “Whitening”? It reminded me of being told by bigots that my parents had “polluted” my white heritage and “diluted” my black heritage.

But, as I continued reading, it became clear that those concerns were coming from a very different perspective than the racism I heard in my youth. The Kent University study is not a thesis against interracial relationships – far from it. It highlighted, perhaps for the first time, mixed-race people sharing feelings about their own children and identity that they also acknowledge sound irrational, unwelcome and self-contradictory.

One mixed-race participant, “Abike”, reflected on her own son and his white partner, saying: “I’m aware in the awful sort of way, almost like some horrible eugenicist, their children will be just kind of completely white. Which is kind of odd, I sort of think … and I don’t know if he ever thinks about that … so … it will be kind of weird.”

Even more interestingly, “James”, in his early 40s, paradoxically feared that his children would adopt the very views that many of us actively encourage in our children – that race is irrelevant: “I think what really bothers me is I don’t want them to forget that race matters. That race affects people’s life chances. I want them to help me and to help the world make it different.”

These are not the words of white racists or black supremacists, but mixed-race people who have a white parent, a white partner and children who interface with the world as if they are white. However unexpected such sentiments seem, there is real honesty and intimacy in how they were conveyed in that study. Most importantly, whatever concerns parents may have about their children’s sense of identity, it will be for that next generation to work it out for themselves. What troubles their parents may not worry them at all.

Facebook Twitter Pinterest The cast of Kwame Kwei-Armah’s series of monologues Soon Gone: A Windrush Chronicle, shown on BBC Four in February. Photograph: Carlton Dixon/BBC

My parents brought me up to believe that racial integration – including interracial marriage – is not only a good thing but is the natural progression of a healthy society. I still believe that. They also taught me that “race” is largely a “social construct” that limits us, and we should strive to see it as irrelevant. But the Kent study and the new generation of mixed-race Britons may force us to question that.

It reveals that many first-generation mixed-race parents do not want their children entirely to ignore or “transcend” race, not least because they see race as part of their cultural heritage. It is as much something to be valued as something to be “outgrown”.

We have always imagined that children discarding a sense of racial identity would be liberating for them. But the Kent study surprisingly suggests it can also result in a sense of loss. Even more bewilderingly, those two contradictory feelings will often exist side by side.

The artistic director of the Young Vic, Kwame Kwei-Armah, believes the story of second-generation mixed-race Britons to be one of the most interesting cultural narratives yet to be told. A few months ago, he produced a series of short dramas, Soon Gone: A Windrush Chronicle, for BBC Four. Each of the eight episodes is a beautiful account of life in the UK for successive generations of people with Caribbean heritage.

The most arresting is the final episode, featuring the story of “Michaela”, the teenage great-granddaughter of “Eunice” who had arrived on the Windrush in 1948. Michaela’s monologue explains how, despite her white appearance, she had always considered herself black, and how she had struggled to express that identity when others did not see it.

Kwei-Armah explains that after considering a number of actors, they settled on rising star Olivia-Mai Barrett. “Her performance was incredible.” he says. “I was amazed at how she brought such insight and empathy to the part.” It was only a few days after the screening that Barrett introduced him to her mixed-race father and black grandfather. He had not even realised that Michaela’s story was her story too.

Matthew Ryder QC is a barrister based at Matrix Chambers. He was deputy mayor of London, leading on social integration