Winsor & Newton produces two black inks: Black Indian Ink and Liquid Indian Ink.
The Liquid Indian Ink is actually sumi ink, ink that's ground with water from traditional Chinese stick ink. This type of ink is meant for calligraphy and lettering work because there's variation in the light and dark intensity within strokes.
The ink comes in a rather small 14ml square base glass bottle. It's really quite small compared to most other ink bottles that are 30ml.
Here are some tests.
The ink flow is good and it dries fast.
When the ink is applied, you'll see lots of particles. It's heavily pigmented and you're recommended to wash your brush or dip pens after use.
As you can see the pigments are not evenly spread out.
It can hold a sharp edge well.
The ink is not waterproof.
This is a ink designed for calligraphy and lettering use. I find the black intensity to vary quite a bit even after shaking the bottle before I dip my brush inside.
If you're looking for a darker sumi ink, I recommend the Kuretake Zig Cartoonist Sumi Ink 60.
If you're looking for something with more visible variation within the strokes, then the Winsor & Newton Liquid Indian Ink is not bad.