Overstaying on single entry visit visa

My friend's visa is already expired on 27th of November, I've shared all the info with him and told him multiple times that overstaying is never a good thing and you might get in trouble, He's working on a job without any contract or work visa, I'm really worried for him,


Kindly share what possible consequences can happen with him if he gets caught, so i can share with him with much clear details, as his "agent" keeps telling him not to worry about anything

He can face jail /pay fine and be deported.

As above.  And they are doing a lot of inspections these days.