Definition von in for a penny, in for a pound im Englisch Englisch wörterbuch
Expressing recognition that one must, having started something, see it through to its end, rather than stopping short thereof; accepting that one must “go the whole hog”
It appears to be a situation where the greenhouse proponents are in for a penny, in for a pound. As long as the myth needs to be kept alive, this is the inescapable conclusion.
() Originally with reference to the fact that if one owed a penny, one might as well owe a pound, as the penalties for non-payment were virtually identical in severity.