I would have suggested a small chair too.

Did it used to be an access door there

Maybe you could reconfigure and maximise the plan of the floor

Unfortunately no way to reconfigure, and no access door, I think it was just poor planning when they originally built the property.
I thought about a small reading area, not sure it would get used much though, although may look nice.
Any other thoughts for a useful space?

What about remodelling it and removing that section of floor altogether? The banister over the stairs could be replaced by a glass banister spanning the full width of the landing, and you would have a wow factor double height hallway. (I have no idea on costs though, or structural issues - so it might not be an option 😂)

Due to large scale windows (1970s property?)  If Reading area will depend on view, roof and neighbours otherwise you allocate an area that will never accomplish function.  Maybe a big plant and a comfortable chair but not big

I would just go for a large pot plant on the floor. The bigger, the better but check the plant’s requirements with regard to the amount of sun that comes in. Some don’t like to be in direct sunlight.

I would use the space to hang a long skinny Boucherouite rug or stacking baskets. Then it will look like it had a purpose. Or a plant of course.

Looks like you get plenty of light there. Why not try growing some edible crops, tomatoes, chillies etc.

What's happening on blues

Here’s a full floor plan for more context

The boxes to the right of the ringed area are cupboards

Thanks for all of your replies! Suggestions in summary:

1) Comfort area: chair+plant

2) reconfigure stairway to have double storey entryway

3) veg/plant area

I think I have decided to utilise the space for a mini office area (provided I can easily get a socket on that wall from the wiring in bedroom next door) - 80cm width desk and a compact chair with a nice desk plant. Any reason this may be a bad use of space?

If you use it for an office, consider how hot / sunny this space might get

Mini office area is a good idea. You can get blinds if sunlight proves to be a problem. The space reminds me of the hallways in flats we had when I worked in a housing association. There were four flats to a block, two upstairs and two down. The stairs and landing were between the two upstairs flats and there was an area just like yours by the window. These were built in the 70s. It proved to be a bit of an issue as people wanted to put things there, but the fire officer wasn’t so keen! Anyway, an office space sounds good to me given it is within your flat. Angie

The living room cupboards are structural? I think you could maximise the livable space and add value to the property

If office area, make space for storage and not big computer otherwise will make it look workplace every time you go downstair. Light will not be ideal for computer screen.

I would suggest one of those tiered plant stands with some striking greenery to brighten it up. Plants always improve any living environment. Not an office unless unless you are really stuck for space.

That's an extremely large glazed area with a not-very-spectacular view beyond. I'm just wondering whether you could block off the lower 2 panes (perhaps with some self-adhesive 'obscuring' material), and then place an appropriately sized cupboard there for extra/ seasonal storage ? Stuff you don't want in your living room or bedroom - suitcases, sports gear ... There will still be plenty of light coming through, especially as your having a glass balustrade. I agree - it was poor design originally !

It would make a lovely compact office/laptop space.

Agree with Little Jem window adhesive on lower half of window would allow diffused light giving a sense privacy making it 'an area'.

Maybe for the top of the window if its possible - two indoor hanging plants? Thinking something low maintained eg. spider plant or mother of pearl?