MADAM, I feel I must take issue with last week's letter headed 'Know your flags'.
It is completely wrong to say that the Union Jack is only flown on a ship leaving port or at sea. In the Royal Navy, the Union Flag is flown from the Jack Staff when the ship is alongside or at anchor or to a buoy, and as soon as the ship slips from the jetty, anchor or buoy, it is hauled down. The flag the gentleman is referring to is the White Ensign, which is flown by all commissioned ships.
There are certain times, however, when the Jack is flown when the ship is under way, i.e. when she is wearing the Royal Standard, escorting a ship in which the Sovereign is embarked, or when other ships in the harbour are dressed overall – but not under way.
This information is taken from my Manual of Seamanship.
Gerry Lewis, Ross