Kell Brook's world middleweight title dream ended in a devastating fifth-round stoppage defeat by the fearsome Gennady Golovkin at London's O2 Arena.

Stepping up from welterweight to challenge one of the greatest middleweights in history, he did his reputation little harm but, as expected, was gradually out-boxed and over-powered by the defending champion.

His pursuit of Golovkin's IBF, IBO and WBC titles - the WBA chose not to sanction theirs - concluded in the fifth when, struggling to resist the champion's latest powerful assault, Brook's corner threw in the towel.

Referee Marlon Wright responded by waving the action over, and while the crowd booed and Brook complained, he was swiftly tiring and it appeared the right decision.

The 30-year-old's finest chance of victory came in relying on his greatest strengths - his impressive punch accuracy and exceptional timing - and hoping he retained his natural power at the bigger weight.

Golovkin has been known to allow his opponents to land unnecessary punches but on this occasion it was Brook's guts and class that created the moments where he enjoyed success.

The champion's masterful footwork - Brook's lateral and head movement proved limited - also repeatedly forced the Briton to where Golovkin wanted him, setting up the lethal attacks that gradually wore his tough challenger down.

Brook was taken to hospital and confirmed that he suffered a broken eye socket. His promoter Eddie Hearn posted an image to reveal the injury.

"I'm out of the hospital. I need operation next week but I will be fine and I'll be back. Sorry I couldn't bring it home tonight," Brook told his followers.