I can't remember the last time I saw one of these. These used to be as ubiquitous as the digestive and rich tea (which incidentally, the finger version seems to have fallen out of fashion too, and they were much better than the round version).
It looks like if you want this biscuit now, you have to search it out. Why did they stop being sold in supermarkets?
Edit: there is one mention of them on Wikipedia about being a variant of Rich Tea. https://en.wikipedia.org/wiki/Rich_tea
These were a staple for me in the 90s.