In a recent blog I wrote about how Meccano deliberately sabotaged the instructions to make kids use their intuition to solve problems. Well I think it's only fair that if we hit problems we share the solutions.
Therefore, my solution today is the following:
Make sure the feature you are trying to implement is present in the release version of the software you are actually using.
It may not be the first time I have made this mistake - but I hope it's the last.