SVN revert!

Tortoise:

Undo changes:
Tortoise SVN -> update to revision -> select revision -> RIGHT click -> revert to this revision.

Undo 1 change
Tortoise SVN -> Merge -> Reverse Merge (tick) -> select revision to remove

Command line:

Reverse Merge

Situation: Trunk was good upto 497 and now its all gone wrong. To revert everything and set the HEAD back to 497 do:
svn merge -r HEAD:497 .