I found an interesting article from a few years ago on the Beeb the other day. Back in 2004 Professor Dame Nancy Rothwell, now President at Manchester, lamented the number of people being promoted to professor.
"I am worried about the potential decline in what being a professor means"
At that time an astonishing 9.7% of academics held the title of professor. Richard Wilson from Loughborough asserted that many promotions were nothing but rewards "for being instruments of the university's administration".