Onlookers claim that Danny, 22, and Alexandra, 21, were “all over each other”.
One reveller said: “Alexandra and Danny were all over each other. They couldn’t get enough of each other, kissing each other’s necks and flirting like love-struck teens!”
During the evening Alexandra drank champagne, while Danny stuck to pineapple juice.
Although the pair entered the club separately – with the ‘Bad Boys’ singer arriving with two friends – they had earlier been for dinner together at Cottons in north London.
It is believed the pair met at a Topshop event in May and kept in touch.
A source said: “Alexandra has liked Danny for a while, and thinks he’s pretty hot. They stayed in touch after meeting in May and finally got around to going on a date.
“It went well and they did kiss, so maybe there’ll be a second date.”
And Alexandra hinted at their romance later that evening by tweeting: “Hmm life is sweet! Life is such a flirt.”
Since his 21-month romance with ‘Piranha 3-D’ star Kelly ended, Danny has been spotted out with several famous women, including troubled actress Lindsay Lohan and ‘90210’ star Jessica Lowndes.
Alexandra has been linked with several men since finding fame after winning Simon Cowell’s pop star search show ‘The X Factor’, including a personal trainer, a club promoter and MTV presenter Rickie Haywood Williams.