Bounding box for rotated markup

[Thomas Morley]

Hi,

please consider following code:

pol = \markup \polygon #'((0 . 2) (10 . 0) (10 . 20) (0 . 22))
\markup \override #'(box-padding . 0) \box { \pol \rotate #45 \pol }

See attached image.
How to get \box tight to the rotated polygon?

Thanks,
  Harm