She is the British sensation who is dominating American R&B. Her music has been nominated for six Grammys. She has been signed by Sony, written for Michael Jackson and worked with Dr Dre and Justin Timberlake. Yet mention the name Marsha Ambrosius to any self-respecting music fan in Britain and, chances are, it will be greeted with brow-furrowed bewilderment.
The Liverpool-born Ambrosius has taken America by storm after her debut album sold 96,000 copies in its first week, flying to the top of America's R&B chart and ranking second in the overall billboard chart. It was flanked by Adele and Mumford & Sons, making it the first time three British artists have dominated the US chart since 1985.
But unlike her chart rivals, Ambrosius remains something of an enigma back home. Her first flirtation with fame was as one half of the soul band Floetry, whose most successful record barely reached No 73 in Britain eight years ago.
All that will change when she embarks on a UK tour later this year.
Ambrosius, who was an assistant in Camden library, north London, while trying to persuade the music industry to take her seriously, admits that things in Britain have been slow.
"I just about made the cover of the Liverpool Echo recently. I wish my grandmother had been alive to see that," she says, speaking from the back of her tour bus bound from Cincinnati to Cleveland, part of a 24-date tour of the US, performing to more than 10,000 fans each night.
A number of British stars have tried to conquer America without luck. So what does Ambrosius have?
Music critic Nick Coleman says: "America is the home of all post-war R&B derived music. Anything we've done since 1956 is a copy, variant, or, in absolutely exceptional cases, an improvement."
It is Ambrosius's tweak to the R&B tradition that has led to her popularity. Her music, doesn't come from the cotton fields of America. It is shaped by growing up in Liverpool and London. Her song Far Away tackles the tricky subjects of bullying, gay-bashing and suicide, definitely not the standard menu for R&B.
She and former musical partner Natalie Stewart, a teenage friend from Brixton, started out as Floetry. "We used to be touring across America for up to nine months a year. The only reason I used to come home to England was for Christmas, to renew visas, or play the one-off gig to a small crowd of regulars in the Jazz Cafe."
The two parted for "artistic and personal reasons" in 2006. But with Stewart releasing her debut solo album last October, it means the two artists will be fighting to retain the love of America that first propelled them to fame. "There's no love lost," Ambrosius concedes. "But I wish her well."
At 33, Ambrosius is on the way to fulfilling her teenage ambitions. One, of course, remains: winning popularity in the country that, 12 years ago, forced her to seek it elsewhere.