An intruder who repeatedly sneaked into an Australian office to eat, wash and sleep has been caught, by a tiny camera hidden in a box of cereal.

Bosses at the office became suspicious after noticing they got through an odd amount of cereal and milk each night and that the sofa cushions were often in the wrong place.

Thinking staff might be using the office for illicit late night liaisons marketing boss Doug Chapman set up a hidden camera to catch them in the act.

But when he played back the footage he saw an unknown late night visitor slipping into office via a ventilation panel, helping himself to up to six bowls of cereal and settling in for a nap on the company couch.

The man also washed up the dishes and put them away before leaving ... making him more productive than some of the members of staff.