This is a significant issue with Thameslink being "performance-polluted"
with delays from Southern; the evidence is clear now that northern
Thameslink trains are starting at St Pancras and performance appears to
be very good.

I've heard that the northern section seems to be pretty good but what is the
general opinion on the southern section? The limited exposure I have to it
suggests that performance improved for couple of months but this month
things have been a bit ropey.