Niall Horan is back with his ex-girlfriend Barbara Palvin

A source told The Sun newspaper: "Being either a working model or performer is incredibly difficult on a relationship.

"In either job you won't be in one place for more than a few days at a time.

"Add to that the fact Barbara lives in America and Niall's base is in London and you've got a logistical nightmare."

The source added: "Barbara's a lovely girl, though. She's completely down to earth and not vain at all, which is what Niall finds so appealing."

The pair first started dating after last year's 'X Factor' wrap party in December and they celebrated New Year's Eve at a pub in Hertfordshire, before breaking up before Valentine's Day.

The stunning model, 20, confirmed she had split from Niall by posting a photograph of herself and a new secret guy on her Instagram account, clutching a bunch of flowers, accompanied with the caption, "Early Valentine".

The Irish star, 20, who now appears to have got back together with the model, is on a break a three-month break after touring the world with his bandmates Harry Styles, Zayn Malik, Liam Payne and Louis Tomlinson.

After the show on Tuesday the Hungarian model and Niall made their way to nightclub Funky Buddha in Mayfair, where they were joined by 5 Seconds Of Summer and bandmate Liam, who had been watching Beyonce in a box with Lily Allen at London's O2 Arena.