Lawyer Gaile Walters has no time for the British monarchy but still believes the wedding of American actress Meghan Markle to Queen Elizabeth's grandson Prince Harry marks an important moment for Britain's black community.

"It has to be significant. The fact of someone black being married into the royal family represents a widening and a diversion and an inclusion that it's never had before," Walters told Reuters as she shopped in Brixton, south London.

"I'm still not pro-monarchy at all because I don't think anybody is born to rule. However, I do understand symbolism and this is very powerful."

The upcoming marriage of the British prince, sixth-in-line to the British throne, to Markle, whose father is white and mother is African-American, has been heralded as demonstrating how Britain has become more egalitarian and racially mixed.

Just 60 years ago, marrying a divorcee was considered unacceptable for a British royal, and only in 2013 did it become permissible to wed a Catholic without being removed from the line of succession.

So Markle's entry into an exclusively white royal family, who wield hugely emotional symbolic power in Britain, should not be underestimated, said Afua Hirsch, author of "Brit(ish): On Race, Identity and Belonging".

"It represents a real change in the messaging to young people growing up in Britain and that idea that blackness and Britishness are mutually exclusive," she told Reuters.

"I think for me when I was younger that would have made a huge difference to me psychologically in my sense of legitimacy and confidence that this is my country."