I live in Dublin in a section of an old orphanage ("The Birds Nest"), which is quite a large building but surprisingly has no downpipes at all in the front of the building, which I'm guessing is about 50 metres long. The water all goes over a valley which unfortunately is in our part of the building. When there is heavy rain it sounds on the top floor as though a large river is running overhead.
I asked a roof expert some time ago if it would be possible to insert a downpipe in the front of our part of the building, but he thought this was impossible because the guttering is cast-iron.
I'm wondering if this opinion is the last word on the subject?