Doctor Who and the State of Decay

In 1982, State of Decay was released as a novelisation by Target Books under the title Doctor Who and the State of Decay.

Cover blurb
The Doctor, Romana and K9 - and a young stowaway called Adric - are trapped in the alternative universe of E-Space.

Seeking help, they land on an unknown planet - and find a nightmare world where oppressed peasants toil for the Lords who live in the Tower, and where all learning is forbidden - a society in a state of decay.

What is the terrifying secret of the Three Who Rule? What monstrous creature stirs benaeth the Tower, waking from its thousand-year sleep?

The Doctor discovers that the oldest and deadliest enemy of the Time Lords is about to spring into horrifying action.