rainwater drain blockage

[stuart noble]

Where a plastic rainwater downpipe goes straight into the ground, does anyone know what happens next? The downpipe appears to be solvent welded on to a white ceramic pipe at ground level but whether this just goes to a soakaway or a proper rainwater drain I don't know. If there's a right angle turn reasonably close to the surface, I might cut out a section of plastic and rod it (difficult to get your arm down there). Anyone any experience with this? The house was built in 1898.

[BillR]

There may be an underground trap before it goes into a drain i.e. an S bend

[stuart noble]

It doesn't drain into the main sewer and I can't see any other drain covers to lift anywhere near the property.