Allegedly is a commonly used phrase and Running joke which has been used/joked about in many different episodes on Have I Got News For You. The joke is used by either Ian, Paul or the Guests of the week, after joking/ making some kind of libel comment, in order to skirt around the rules. Ian is Particularly famous for comments like these having gained the title of most sued man in British legal history.
A common version of this joke is to refer to the programs lawyer after making a risky comment. Ian often pretends to wave at the layer or references the joke being made to test if he's awake. Paul and Ian often refer to comments that won't make it into the finished program.
To be added - Feel free to add.