Can anyone please confirm my thoughts on a drain gulley?

I was clearing a gulley yesterday and noticed some braided packings in
between the gulley and the drain pipe below. Half of the packings appeared
to be missing, leaving a gap of about 10mm between the gulley and pipe
around half of the circumference.

Questions:

Is this packing usually there, or is it a bodge to fill a gap made at
installation or subsequently?
The standing water level in the gulley appears to be just below this joint
in this and other gulleys. Am I right in thinking that the level of the
trap is set such that standing water is below the gulley to pipe joint?
I presume that I should be trying to re-seal the joint. If so, should I
remove remaining packings or try to gob round? What sealer should I be
using if at all on the remaining open joint?

TIA

Phil