South African High Commissioner Cheryl Carolus said the event has been in the pipeline for two years but permission to close Trafalgar Square to traffic was granted only on Wednesday.
Former president Nelson Mandela is expected to be in the audience for the Trafalgar Square concert - it will be sealed off specially for the event.
South African High Commissioner Cheryl Carolus said the event has been in the pipeline for two years but permission to close Trafalgar Square to traffic was granted only on Wednesday.
About 30,000 people are expected to pack the square for the concert which will run from 17:30 to 21:30 BST.
"We have sat around tables for weeks, sometimes until two o'clock in the morning," Ms Carolus said. "I acquired a good few grey hairs in the process."
All the artists will be performing for free and the concert will benefit the Nelson Mandela Children's Fund and The Prince's Trust.
'Family event'
Other stars on the bill include South African a capella group Ladysmith Black Mambazo, jazz trumpeter and political activist Hugh Masekela and pop band Atomic Kitten.
The organisers are keen that the event is not seen as the usual kind of rock concert.
"We don't want a crush. We really want an event that will be a family event, one that will be enjoyable and safe for everybody."
The concert is part of six weeks of festivities which will bring the best of South African talent to Britain as testament to the "vibrancy" of South African culture since the first democratic elections in 1994.
Highlights include performances of a Zulu version of Shakespeare's Macbeth at London's Globe Theatre and the National Film Theatre will hold the first season of South African films to be held in the UK.
And a gala concert of South African musicians, actors and comedians is planned for the Royal Festival Hall on 27 May.
Leeds and its twin town of Durban will be hosting a separate Celebrate South Africa day on 30 April - all testament to the UK's interest in the new nation.
"I'm still greatly moved by the extraordinary goodwill that still exists and the wish for our democracy to succeed," Ms Carolus added.