Add me to the list of people who got the theme early although LOI was 20,23! I used some coarser 23s at numerous times when solving this, leading to admonishment from my other half, to which I replied “sorry but it’s Paul”.
I had to go slowly and carefully through this thread to land 20,23. Thank you for the hints. Maybe I had heard of the phrase in the distant past, but it didn’t click.
Papal cigar is fantastic! Shame there wasn’t room for something involving violins and parasites... (12)... ;-)