Sara and Lisa become £25,000 richer

Sara and Lisa each became £25,000 richer tonight after playing a game of Prisoner's Dilemma.

After the group had nominated face to face, Sara and Lisa received the most votes and were told by Big Brother to go to the task room in the garden.

After being hugged by their fellow housemates, the pair entered the room and were told by Big Brother that one of them could win £50,000, which would be separate from the prize money.

The duo looked at each other in shock and giggled as the housemates in the living area watched on the plasma screen. "Oh my God, how amazing is that?" Rex grinned.

Big Brother explained that they must play a game of Prisoner's Dilemma. Each of them had a block with the word "share" and a block with the word "take". They were informed that they must choose one.

They were then told that if they both chose share, they would win £25,000 each. If one chose take, that person would win all £50,000. However, if both chose take, they would both leave with nothing.

The pair were given a minute to discuss their decision and immediately agreed to share. "I've got a heart of gold," Lisa declared, before adding that Sara was her "best buddy" on the show.

When Big Brother asked the housemates to choose their blocks, they both stuck to their word and chose share, meaning that they each won £25,000.

They immediately started laughing and screaming, while Lisa ran over to hug Sara and pick her up in the air.

"I can't believe it!" Sara yelled.