The Tudor flag at sea
"The characterist flag of the reigns of Elizabeth I and James I was the striped ensign, which developed out of the striped deck level flags used on the ships of Henry VIII's navy.
Both the word 'ensign' (of which a 16th Century variant was 'ancient') and the use of striped flags seem to have originated in military use; the earliest sea ensigns were mounted on deck and removable, staff and all, for use on land.
By the end of the century, striped stern ensigns were common on European ships and those of English ships were often distinguished by a cross of St George in a canton or overall. To judge from the scattered evidence of illustrations, the colours of the ensigns varied from ship to ship; although red and white (the colours of the cross of St George) and green and white (the Tudor livery colours) were used, there seems sometimes to have been no significance in the colours chosen."
*text source: Flags at Sea, Timothy Wilson, Chatham Publishing
*picture shows a Flag Studio vintage example of the Tudor livery ensign, fully stitched using wool / linen mix UK MOD spec fabric.