Another mystery

Freemasons are aghast that the bosses of the Metropolitan Police have made them a declarable institution. No more favours for those who can do a funny handshake? Unless the judicial review goes in the Masons’ favour.
p.s. The first thing I thought on seeing a picture of a cup of frothy coffee with a Masonic symbol stencilled on it was: “Is that the Loch Ness Monster?” The shape in the diamond-shaped frame sure looks like it!