Imperial measurements

Busy day today,  breakfast in St James’ Park cafe at 8am, back home and then lunch at The Bakehouse near Chelmsford and I’m just about to head back into London for dinner at Mortimer House Kitchen. I don’t usually fill my diary like this, but it’s based on the availability of friends.
After breakfast I walked from St James’ Park to Holborn to catch the tube home. I stopped off at Trafalgar Square as I had heard about some brass plaques there. 
Sir George Airy created 3 copies of the official units of measurements after a fire at the Palace of Westminster destroyed the old ones. 
My photo shows 1 foot, 2 feet and an Imperial yard. I would have liked to look at the plaques for the Chain, the Perch and the Pole but some sort of  maintenance work meant they were cordoned off. Maybe next time.
If you’re interested the other 2 copies are in the Great Hall of The Guildhall in the City and the Royal Observatory at Greenwich.