Justin Bieber's 'UK meltdown was over Selena Gomez split'

According to friends, the end of his two-year relationship with the 20-year-old actress left him devastated and he hurtled off the rails, the Mirror reported.

Selena Gomez and Justin Bieber

"He was crazily in love with her. She kept him grounded. She's been a tower of strength through all the hysteria of being one of the world's most famous pop stars. To lose her was like losing an anchor," one pal said.

The ‘Baby' hitmaker's troubles burst into the open last week. u00a0He was two hours late for his show on Monday at the O2 arena in London.

He collapsed on stage with breathing difficulties at the same venue on Thursday, and the following day he tried to fight with a photographer.

A source close to the teen popstar said that he simply hasn't been the same since he split from Gomez.

"It really broke him. They were together for such a long time for two people so young. He hasn't quite known what to do without her. He is lonely," the source added.