Still critics said the Canadian star, who turned 19 on Friday, risked alienating fans by behaving with the same disregard for timekeeping as more hard-edged rock stars.
John Aizlewood in the Evening Standard newspaper said Bieber had shown contempt for young fans, leaving them "exhausted, disillusioned and probably late for school this morning."
Bieber, who is due to play three more nights at the venue Tuesday, Thursday and Friday, has been photographed out on the town several times during his current British tour.
"Since I have been here it hasn't been easy with the press at times but I have loved it," Bieber tweeted.
"I never have any intent to upset or let anyone down. And I'm not okay with things being exaggerated. Once again sorry for anyone upset."
He promised that he would put on a "great show" Tuesday — and it would start on time.
The 02 said Bieber was scheduled to go onstage at 9 p.m.