Big-Ben-Tower

I that am lost, oh who will find me?
Deep down below the old beech tree.
Help succour me now the east winds blow.
Sixteen by six, brother, and under we go!

16 x 6 = 96

Elizabeth Tower, the new name of the Big Ben clock tower since 2012 (renamed for the Queen’s diamond jubilee) is 96 meters high…

It is listed in Mycroft’s notebook in TLD, presumably as one of Sherlock’s bolt holes or places to be monitored:

Pic pinched from @darlingtonsubstitution

In the Musgrave ritual, the treasure was hidden under the spot. What was hidden under Elizabeth Tower in TEH? A bomb.

Are we being told the same story over and over again? That Sherlock has to save himself (aka England)? Or John?