so which biscuits are best for dunking in tea?

ginger nuts are good because they are quite solid, dense biscuits, so you can dunk them for quite a while without fear of them falling about.

Rich tea biscuits are also good, they go soft quite quickly though so you have to just quickly dip them in the tea and eat them straight away. Possibly the best taste though.

Any biscuit with chocolate on is clearly inappropriate.