The message
from The Natural Philosopher contains these words:

Water runs down the inside of your exterior brick/stonework during heavy
rain...

It bloody well should NOT. If it is you have a serious problem.

Though provision is made here
http://tinyurl.com/ozshd
on page 37ish for not filling cavities right up to the oustide leaf in
many parts of the country because of the risk of water penetration.

--
Skipweasel
Pay no attention to the man behind the curtain.