As a square this is nothing special really. A patch of grass with a few slightly sad flowers, redeemed for some by a basket ball court in good nick and in use. The square is surrounded by grand houses, many of them converted into hotels. I couldn't give recommendations. There was a mix of people using the grass to sit, including a few drunks.
Not a place I'd choose to eat my lunch normally, but grass is in short supply in some areas. Conveniently close to King's Cross and St Pancras stations, so nice to know about if you are passing through and desperate for somewhere green to sit. Or if you want to shoot a few hoops read more