'Doctor Who: Leviathan' is a audio play based on a long lost unproduced 80's TV script written for Colin Baker's Sixth Doctor. It stars Colin and Nicola Bryant as Peri. It is a double CD set consisting of 2 episodes of around 55 minutes, plus interviews on the end of each CD. It is really good, with an excellent story and cast. I can't believe it's under a fiver, these CDs usually go for around a tenner!