from what i understand, the mail and sun are the two most influential papers in the country, one broadly marshalling the working class and the other the middle-ish. middle-ish more likely to vote therefore politicians absolutely desperate to keep in with the mail.
and every newspaper i have worked for over the last fifteen years or so has at some point said to me 'can you make it more Mail-y?', such is there influence over their peers.
it really is huge, tbh. and not to be under-estimated.