Attending a party organised by Radio 1 DJ Nick Grimshaw, the One Direction singer and the youngest daughter of Bob Geldof and Paula Yates spent most of the night together, according to The Sun.
A source claimed: "Harry has become big mates with Nick and was invited out with some of his Primrose Hill pals.
"He'd only been back from America for a couple of days but still fancied a night out."
The insider added: "He wanted to carry on his birthday celebration and he knew that with this lot he'd have an interesting time."
Styles, now 18, confirmed his separation with Xtra Factor presenter Caroline Flack on Friday, January 27.
> One Direction Harry Styles, Caroline Flack 'haven't ruled out reunion'
Watch the video for One Direction's 'One Thing' below: