The message
from "r.bartlett" contains these words:

Our drain runs from our garden to next door and away. It appears that the
section on their ground has collapsed or at least particially blocked where
the ground has dropped. Thus in less than 2 weeks I'm paddleless!

However as it's 'my' waste but the drain is on their land who's
responsible??

Try a google. This sort of problem has been aired in the past.

FWIW I seem to remember that for shared drains to be public they must
have been laid before some date in the 1930s, perhaps 1936 and that, if
it is a private drain, all connected to it have a joint responsibility.
Memory however is sometimes faulty.

Some years ago my father was in the same situation but on the opposite
side of the fence. He shared the cost of repair with his neighbour even
though the blockage was upstream of his connection. I would know whether
the situation would be different had he not had a connection to the
drain.

--
Roger Chapman