VCS with locks

It helped that other branches of the same organization (for 'other
branches' read 'sitting across the room') had been convinced by these
auditors, so were using SCCS with a horrible shell script wrapper to
attempt to provide some semblance of branching, and auditor-imposed
constraints to prevent reservation in a wide variety of situations (such
as a single client out of hundreds querying something in *any* previous
change touching the same file: want to make an unrelated change touching
such a file, got to find a way to make it in a different file instead!),
so everyone talking to the auditors knew *exactly* how horrible their
proposed golden age would be.