They have always had a strong slant on investigative journalism. The whole back section (and quite a lot of the front tbh too) fall into that. The writing can still be acerbic but the journalism is hard hitting.
They continue to honour one of their very earliest columnists with "The Private Eye Paul Foot Award for Investigative and Campaigning Journalism". It's a big part of the magazine.
https://www.private-eye.co.uk/paul-foot-award