swan caught with fishing line around its leg - what to do?

went out feeding the swans today and spotted this on one of the swans:

looks like abit of fishing line caught and tangled on its leg. someone else spotted this too. it doesnt look like in distress though, but i know with something like that on its leg, the line might be thin and sharp it might cut through its leg. when the tide's not there the swans walk on land alot and i fear it may struggle.

this is at the river thames. i live in kent.

who should i contact - the RSPCA, RSPB, or my local council? not sure whats the proper procedure?

i tried to lure the swan to me with food with the [foolish] hope of being able to get the thing off it but swan didnt wanted to come close.

swan is with a group of other swans.

there are guys that fish where i go to feed the ducks. it angers me seeing wildlife being the victim of our trash. i wish i could tell people to be more responsible - the problem is, if tried doing that here you'd risk being assaulted by them. people are just nasty here.

thanks