Incident on Saturday, ball unpayable in bushes.
OK, we got it wrong. The drop rule is from the point where the ball lay, not the nearest point of relief. So should have gone back and replayed the shot on penalty of 1, since not possible to play from within 2 club lengths (still in bushes) nor go away from hole along line, as far as necessary (would have been Therfield).
You can deem a ball unplayable anywhere on the course except when it lies in a water hazard (lake, pond etc.).
You have three options if deeming a ball unplayable all under a penalty of one shot:
A) Play again from where the last shot was played.
B) Drop the ball within two club lengths not nearer the hole
C) Go back as far as you like keeping the point where the ball lay between you and the hole.