How to specify the width of margins around a TGraph?

For a TGraph, I would like to be able to specify the margin width, i.e. the distance between axis and pad boundary (for PAW-oldtimers: the equivalent to SET XMGL and SET YMGL). This, in turn, to be able to fit in an axis title with a larger font size.

How can I do that? Thanks for any help.

Well, in the meanwhile I found the answer.
Let me post it here, for the sake of completeness: