Chiwetel Ejiofor and Thandie Newton brought together Hollywood and Nollywood for their premiere of Half Of A Yellow Sun.
The film, in which they play a couple, is adapted from the book by Chimamanda Ngozi Adichie, set in Nigeria during the struggle to establish an independent republic.
Ejiofor, who was nominated for an Oscar for his performance in 12 Years A Slave, said the book and film held a personal significance.
He said: "It was incredible, I spoke to my grandfather a few years before he died. The conversation took a turn towards his experiences in the war and we ended up doing 10 hours of interviews about it.
"It very closely followed some of the events in this film so I was very moved and engaged to make this film.
"It was a very emotional and powerful journey for me."
The 36 year old also spoke about how pleased he was to play opposite old friend Newton for the third time.
He joked: "Two times boyfriend and girlfriend and this is our first marriage so we'll see where it goes from here."
Newton, 41, added: "This is our third time playing lovers, I think we finally got it right."
She went on: "I've known him for many years, I worked with him on his first film 13 years ago.
"This was a deeply personal film for him and I thought I knew him but I realised while we were shooting that I was getting to know him in a whole different way."
Run, Fatboy Run star Newton also said she had been pleased to see her pal do so well during awards season for 12 Years A Slave.
She said: "It was like seeing a family member up on stage. I actually worried about him having to do so much travelling and press, how exhausted he must be.
"It was very well deserved and it's been a great year for him."
The film's other stars including John Boyega, Joseph Mawle and Babou Ceesay, as well as novelist Adichie, director Biyi Bandele and producer Andrea Calderwood, were also on the red carpet for the premiere at Streatham Odeon last night.
Half Of A Yellow Sun is released in cinemas on April 11.