International maritime signal flags is a set of specific signal flags used for visual communication between ships and vessels in the seas and oceans. These flags are used to broadcast the so-called International Code of Signals (MKS for short), which was approved in its current form in 1969. Most signals are 1 to 3 letters long, with each flag assigned a Latin letter. Moreover, each letter has been assigned a specific meaning. For example: a flag composed of two yellow stripes and one blue stripes is the letter D (Delta), which is assigned the meaning "Stay away - I am maneuvering with difficulty". On the other hand, the flag with two black and two yellow squares is the letter L (Lima) and means "Stop your ship!". However, the MCS also enables letter-by-letter communication, where the flags are assigned only a letter meaning, with no additional meanings.
The flag of the Royal Navy, i.e. the British Navy, was and is the so-called White Ensgin. It is a white flag with the St. George, and in the upper left quarter is Union Jack, the flag of the United Kingdom. The flag is used on all Royal Navy ships, yachts included in the so-called The Royal Yacht Squadron and some Trinity House units. The genesis of the present Royal Navy flag dates back to the beginning of the 18th century, when Scotland and England with Wales were joined by the real union into one kingdom, which led to the change of the flag of the new state. Thus, the current flag of the Royal Navy using primarily the Holy Cross. George was changed with the addition of elements of the Union Jack flag. It is assumed that such a flag was used for the first time in 1707. Since 1864, such a flag has been reserved only for Royal Navy units and cannot be used - with exceptions - by merchant navy ships. It is worth adding that the White Ensgin flag influenced the shape of the navies of such countries as Australia, Canada, India and South Africa.