The picture is very difficult to gain a sense of orientation from. Is it taken from the bottom looking up? If you look to the left of the hose labeled No 3 you can clearly see the radiator fan motor and to the right of that same hose is a glimpse of the radiator matrix. At the top of the picture is what looks like part of the bell housing/gearbox casing, but, if it is then it's the "wrong" way round to my mind, because the gearbox is on the left side (passenger side on our right hand drive vehicles) whereas the gearbox looks to be on the right of this picture?
So I'm very confused. Can you take some more pictures maybe from further out so we can see some more recognizable components and maybe from the top too?
If I had to take a bet on it I'd pick hose No 2 as it does seem to be connected to the "bottom" radiator tank - I think? However I'm well known for loosing bets!
Another thing which is just slightly puzzling me is that our radiators are mostly - maybe exclusively? - crossflow (water goes side to side) but this picture, if I've got my orientation right, seems to show the flow would be up/down? That's why I'm saying more pictures from further away could help. I don't recognize that circular component to the left of hose 2 either? but then again I'm not familiar with the diesel variants.