Outside the nautical sphere, ensigns are used to designate many other military units, government departments and administrative divisions.

If flown while underway, the ship must be dressed for a special occasion or celebration with masthead ensigns, otherwise it signals that the monarch or an Admiral of the Fleet is on board.

The use of the Union Flag as an ensign on a civilian craft is still illegal, unless it has a white border,[1] ever since Charles I ordered it be restricted to His Majesty's ships "upon pain of Our high displeasure"[This quote needs a citation] in the 17th century, mainly due to its unauthorised use by merchant mariners to avoid paying harbour duties by passing themselves off as royal vessels.

Since the reorganisation of the Royal Navy in 1864, use of the White Ensign (a red St George's Cross on a white field with the Union Flag in the canton) has been restricted to ships, boats, submarines and on-shore establishments of the Royal Navy.

The Blue Ensign (dark blue field with the Union Flag in the canton) undefaced is worn by masters of vessels in possession of a warrant issued by the Director of Naval Reserves, and by the members of certain yacht clubs.

The master must be of the rank of lieutenant RN or above, and fishing vessels must be crewed by at least four other Royal Naval reservists or pensioners.

Under the terms of a Memorandum of Understanding with the Ministry of Defence,[2] officers of the Sea Cadet Corps hold their ranks as (SCC) RNR on a 'nominal honorific' basis, and are included on the Navy List as a courtesy (though they are not commissioned, but 'appointed' within the Corps).

Other defaced ensigns were used by vessels of the Port of London Authority, Mersey Docks and Harbour Board, the Humber Conservancy, Custom House, the Board of Trade, Lloyd's of London, the Post Office, submarine cable laying ships, and other departments including War Office Ordnance.

The Red Ensign undefaced is for the use of all other British merchant navy ships and private craft.

The flag of Hawaii is a British ensign with a background of white, red and blue stripes.

The white ensign of the commissioner of the Northern Lighthouse Board is unique in that it remains one of the only examples of a pre-1801 Union Flag in official use today.

More unusually, it is the Union Flag canton rather than the fly which is defaced with a modified Southern Cross.

There is some evidence of the existence of a Green Ensign in British Ireland, defaced with a gold Irish harp in the fly.

This flag is an orange ensign defaced with a white shield, and a red maple leaf within it.

This squadron did not actually exist but was a term used unofficially to describe those naval personnel who worked ashore or did not have a ship.