How to delete (tmutil delete) all old backups from TimeMachine - keep only current full backup

How to delete (with CLI tmutil delete) all old backups from TimeMachine. I wish to keep only current backup. I wish to put that into crontab. Found How to Delete Old Backups from Time Machine on Mac sudo tmutil delete /Volumes/Time Machine Backups/Backups.backupdb/MacBook\ Pro/2015-07-13-150021/ I don't like to specify Timestamps. I wish to have only one current full backup. This means remove deleted files and versions from backup disk.