What is this pipe for? (Piglet John or similarly helpful people do you know?)

[Battybonkers]

We get a big puddle on the patio outside the front door so I wondered whether this was some kind of drain that might help - It was full of mud so I started excavating and got as far as my elbow - and gave up. Should I keep going? it doesn’t seem to connect up to the gulley (pictured) so far.

Is it a vent to the drains? We had one that had been cemented over and started to get foul waste coming up via the sink drain. Once the cement was removed it was all ok.

Maybe - I hadn’t thought of that. It probably shouldn’t be full of mud in that case!

We have similar in our back garden on the way out to the public sewer. It is a drain for the outside of the house that goes into the sewer. our down pipes don't align with it either. Perhaps yours is the same?