Was Nathan fed up with the house?
Was Nathan fed up with the house? Paul Broben

Mystery housemate walks out of Big Brother house

A BIG Brother housemate has walked off the show.

Social media is tipping Nathan as the dearly departed housemate, with one Twitter users claiming to have spotted him smoking at Dreamworld yesterday during a ride on the park's steam train.

All will be revealed on tonight's show, with the Big Brother live feed suspended to build anticipation.

Nathan, the male intruder whom the public voted to keep in the house, had admitted to having issues with coping with the isolation of the show last week.

But Wednesday's evictees Katie & Lucy, the ever-positive Sugar Sisters, seemed to think he was doing alright.

"We've chatted to Nathan and we absolutely love him," Katie said.

"He's really down to earth and we had lots of fun with him. I think he's coping really well."

The show's official Twitter handle said one housemate has "sacrificed themselves for another" and that their identity will be revealed on tonight's show, which airs at the later time of 8.45pm because of a delayed broadcast of Australia's Got Talent following yesterday's NRL grand final.

Producers wouldn't reveal much more, except that the surprise departure is not made by dog George Clooney.

One of the two female intruders, Madaline and Boog, is also supposed to be booted off the show tonight.