Giro died in 1934 from accidental eletrocution (contact with an exposed wire) and although it may seem absurd, he was given a full Nazi burial.
The small tombstone has the German epitaph "Giro: Ein treuer Begleiter" which means "Giro: A true companion".
Nazi Embassy in London
The Nazis had to leave when the war started and The Foreign Office used the building from 1939. They attempted to remove most of the swastikas but apparently there is a border design of swastikas on the floor of one public room.
The building is now occupied by the Royal Society.
It did take me a while to find the tombstone as it's much smaller than normal, but you'll find it under the tree, at the top of the steps, close by the enormous statue of the Duke of York on a tall column. The tombstone is in a small space that was once the front garden of 9 Carlton House Terrace but is not directly in front of the building. It is the other side of the garage ramp.