ristol Beaufort - External Plumbing Query

[INM@RLM]

Outboard of the engines on the underside of the wing of every Beaufort was what appears to be a faired tube running horizontally beneath the wing but which then concludes by sweeping diagonally downwards and ending in an opening.

Two questions
What please was the function of this arrangement?
Where is this described in a published work?

Grateful for all help.