mark one's own homework

English

mark one's own homework (third-person singular simple present marks one's own homework, present participle marking one's own homework, simple past and past participle marked one's own homework)

(UK) To assume the role of evaluating one's doings when a disinterested party is required.
- 2023 November 2, James O'Brien, “Matthew Elliot”, in How They Broke Britain‎^[1], Ebury Publishing:
  Aware that his organisation was to be found guilty on at least four charges, he had tried to mark his own homework by submitting a 500-page dossier to the EC attempting to rebut its conclusions before they were even published.
Used other than figuratively or idiomatically: see mark,‎ one's,‎ own,‎ homework.