Ariana Grande has been spotted leaving Niall Horan’s house in the early hours of the morning.

They were first seen together as they partied in London on Monday night after Grande's gig at the 02 and it looks like they are doing little to stop the romance rumours.

The 21-year-old pop princess was spotted leaving the Irish One Direction singer's Hertfordshire mansion in the early hours of Wednesday after spending five hours inside.

According to sources, Ariana arrived at Horan's home at 10.00pm on Tuesday night before leaving at 3.00am Wednesday morning but despite appearances, a rep insisted was not for a romantic tryst.

Ariana's rep told MailOnline: "Ariana is friends with Niall. He had a big party that she attended."

She appeared to be with some members of her entourage and was picked up by a driver and bodyguard.

According to recent reports, Niall Horan has split from Australian girlfriend Melissa Whitelaw due to the difficulty of maintaining a very long distance romance.