Upvote:3
It might be possible but I do not think his chances are high.
The most important reason countries have visa systems is to keep out people who are likely to work illegally, and for that stay longer than allowed. Having been caught working illegally he has proven to be willing to break that rule.
The UK visa system does not block giving visa to people in his circumstances but it is not usual to ignore previous breaking of immigration laws.
Applying and being denied will hurt future visa applications, so better only try with the right kind of help. The law society https://www.lawsociety.org.uk/ can help you find the needed help.