I bought it for £7.89 from Amazon. It arrived this morning. There is a button on it which I assume is the button for the backlight. The only other thing on the watch is the knob for changing the time. Kept pressing it but nothing happened. Read another review, on the same model but different colour, where the reviewer said the backlight stopped working within 2 weeks.
I started the process of returning it but decided against it as it's too much bother and I don't need that function. A similar fob watch without the backlight is the same price anyway. I chose this one because it had the extra feature for the same price.