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
Ive been searching for a good biscuit for a while now. Simple, clean balanced flavor. And I found it at a Sikh temple out of all places.
The best tea biscuit currently on the market is 'parle g' or 'parle g Gold' super cheap and available in every Indian grocery store.
Its not exactly what you are looking for. But your search will stop after getting some parle g.
I think my family bring those back when they've visited India. There's a chocolate biscuit they bring as well, I can't remember if it's the same brand.
Edit: it's called Hide and Seek and I think it's a Parle brand too.