Hundreds of well-wishers gathered to catch a glimpse of the couple as they visited Reprezent radio station, which is staffed entirely by young people and based in a community-led complex built out of old shipping containers.
In the couple's first joint interview, Meghan spoke openly about changing her life - quitting acting and moving to Britain - for Prince Harry.
On an impromptu walkabout later, she was showered with flowers and cards as she shook hands with the crowd, expertly steered by Harry.
The pair arrived in the January cold with Meghan wrapped up in a grey woollen coat from Smythe and a Jigsaw scarf.
Meghan Markle meets members of the public following a visit to youth-orientated radio station Reprezent FM in Brixton Dominic Lipinski PA Wire
Markle, who once ran a blog and had an active social media presence, had slowly scaled back her activity on the accounts when her relationship with Prince Harry became increasingly serious. "I can see why your show is so popular". "I must tune in".
Kate Middleton's thank you cards to her fans read, 'The Duchess of Cambridge was touched that you took the trouble to write as you did on the occasion of her birthday. Station founder Shane Carey said news of their visit had caused "massive excitement" in the area. "We're having the spotlight shone on us from all the world's media, pretty much, we've never had this attention".
They arrived in a chauffeur-driven auto at the studios of Reprezent FM, a community radio station which trains youngsters in media and employment skills.
When asked how he felt about the impending ceremony at St George's Chapel in Windsor, he said: "I think it's wonderful, I'm very delighted".