Drain

Apodemus

Of course, it is possible that the drain simply goes to a soakaway, rather than actually linking to the main sewer.  If that was the case, slowly seeping away might be the best you can hope for, short of digging the whole thing out and establishing a new soakaway. 

TheProfessional

No other access that I can see toward the road. The pipe I assume goes along the line of the boundary wall and to a pipe under the pavement although no evidence of that. I'm waiting for my long gloves to come before sticking my hand in

There is access on the other side of the driveway to what I assume is the sewer pipe on the other side of the house (rain and main bathroom soil pipe) picture below 

Jeepers_Creepers

It has been known for drains to have bends and even to cross in a diagonal direction.

Have you lifted that cover? What?! No?!!! :-)