Any idea what this is likely to be?

[MortenHarketsarms]

This wooden structure has appeared right on the boundary with our next door neighbours. Is it some sort of fence or the framework for a garden building? Something else? You can see from the picture how close it is to our sitting room window and I’m worried it might end up with a pitched roof and cut out light. I know I should go round and ask but don’t want to be an interfering neighbour and wondered if anyone here could shed some light? Thanks.

Pergola for a triffid!!

Don’t spoil the moment KidsdoBetter, I’ve allowed myself a brief spell of imagining how lovely it will be when it’s smothered in wisteria and rambling roses…

So, I think it’s no higher than 2.5 metres (though I’m not good at judging distances - it’s actually 12 feet from our sitting room not the 8 I estimated in my first post) and, having gone out to take a proper look, I can see there’s maybe 40cm between it and our wall rather than butted right up to it. I suspect it’s legal and permitted development, though googling suggests they should have served a party wall notice if the foundations are less than three metres from our wall or deeper than the wall’s foundations, which I’m guessing they will be.

I’m getting used to it now from this room - assuming they’re not going to add a pitch - but it’s much more visible from the kitchen, even though it’s further away.