The 24-year-old flew in to take part in this year's Capital FM Summertime Ball on Sunday - to the delight of British fans, who turned out in force despite the rain.
Islington-born Leona took to the stage in front of a 55,000-strong crowd which was treated to turns by Katy Perry, Kelly Clarkson, Alesha Dixon and Lionel Richie. Also joining the lineup on stage was newly reformed boyband Blue.
Enrique Iglesias, who was performing as well, made the day of one lucky lady by pulling her up on stage for a cheeky kiss. Meanwhile Katy, clad in a Minnie Mouse-inspired polkadot frock, thrilled with an energetic rendition of Hot'n'Cold before finishing her set with I Kissed A Girl.
It was literally a flying visit for Leona, as the day after her performance at the fundraising radio event, which was hosted by Lisa Snowdon and Johnny Vaughn, she returned to her newly rented Hollywood Hills residence to continue work on her second album, which is due out at the end of the year.
And so far - she's now more than half way through recording - it's looking good, says the singer, who reveals she's been collaborating with Justin Timberlake and Timberland . "I have got on a lot of songs and I am just really, really pleased with how it is going."