I am trying to remove a SQL 2012 cluster node from a Server 2012 R2 machine. However the windows and cluster itself has already been destoyed so when trying to remove the node the setup is erroring out in validation because ...

"The local computer is not a member of a Windows failover cluster" 

and 

"The SQL Server failover cluster service is not online, or the cluster cannot be accessed from one of it's nodes. To continue determine why the cluster is not online and rerun Setup. Do not rerun the rule because the rule cannot detect a cluster environment".

Does anyone know how to force the removal of a SQL clustered node?