Big Brother will be turned into a prison this week - with half the housemates becoming prisoners, and the other half their guards.

Half the group will be locked into a secret prison block next to the BB house, and will have their finger prints taken before being forced to don their inmates uniforms.

The unlucky housemates will only be given basic rations, and have to carry out mundane tasks, before sleeping on hard beds.

Housemate Prison Officers will be charged with constantly checking up on their charges, and ensuring they do not break the rules.

As reported yesterday, the week will end in another BB twist, with a shock double eviction coming from the housemates' other task this weekend - coupling up with their 'best friend'.