"Chippy" wrote

Its being inside the City was the reason that most royal trains to
sandringham went from Kings Cross, rather than Liverpool Street.

Apparently, if the sovereign enters the City it triggers a host of
ceremonial, with the Lord Mayor required to attend, etc.

But not always. GFF recorded an occasion when he was waiting at LSt to meet
the Royal Train when a message came through that the arm had fallen off the
up starter at Tottenham. He was therefore surprised when the train eased in
smoothly to time. It transpired that there had been no nonsense about
cautioning the driver - a porter was despatched to scamper up the post
holding the signal arm, 'to hold it proudly in the off position while his
Sovereign went by under clear signals'.

Peter