APFS/High Sierra - tmutil deletelocalsnapshots will not delete snapshots - Error parsing argument
I discovered, after hints on the linked thread, that quotes will do it...

TetsMac:~ glee$ tmutil deletelocalsnapshots "2018-07-26-93812 am"
Deleted local snapshot '2018-07-26-93812 am'
TetsMac:~ glee$ tmutil listlocalsnapshots /
TetsMac:~ glee$ 


&amp; it's finally gone.