Common main title of a figure panel compiled with par(mfrow)

Question

I have a compilation of 4 plots drawn together with par(mfrow=c(2,2)). I would like to draw a common title for the 2 above plots and a common title for the 2

Answer 1

The same but in bold can be done using title(...) with the same arguments as above:

title("My 'Title' in a strange place", line = -21, outer = TRUE)