what is this grey box?

[kaygee]

wondered if anyone has any idea what this grey box is outside our home..its a part of the extension that was completed early 90's, there is a drain that runs under the single storey extension here, if its related? the box has holes to the front, it doesnt open and has us baffled..any ideas? View media item 33572 View media item 33573

 

[foxhole]

Drainage vent.

 

[Nige F]

indeed - air inlet for drain . Surprised they left it there and built round it It`s a 19th. century drain component - and most of them are broken or missing altogether