Did you read the rules? Cutting the corner is permissible if the field is grass and not sown or containing livestock.
What?! I could have saved well over a minute then...
Hang on. Section D, point 2: If a footpath runs along two sides of a triangle then runners must not cut across and leave the path.
'Unless otherwise indicated in these rules ...'. See the notes for leg 18. Was it grassy? Blame your more experienced captain for not pointing this out.
Yeah, just plain ol' grass. How annoying.