By this rule the largest ensigns in 1623 were 27 feet long and 16 feet 6 inches deep, and the largest "flags" (i.e. masthead flags) 36 feet long and 22 feet deep. In Pepys' time the ensign or flag of a first rate was 26 breadths and 14 yards in the fly, while the jack was of 14 breadths and 7 yards fly, and the pendant 3 breadths at the head and 32 yards fly. The "distinction" pendant as used in the Downs was broader and shorter, being of 5 breadths and 21 yards fly. The Lord High Admiral's flag was 24 or 22 breadths and 12 or 11 yards fly. In 1708 the ensigns had slightly increased in size and varied from 10 to 30 breadths, but the "breadth" was then nearer 10 inches than 11. An ensign of 26 breadths in 1709 was 14 yards long and the Union canton was 189 inches by 117 inches. In 1742 ensigns were from 16 to 34 breadths and 9 to 17 yards long, and jacks were from 6 to 16 breadths and 3 to 8 yards long.
These were truly enormous flags, and towards the end of the eighteenth century the sizes seem to have suffered a gradual reduction. In modern times the "breadth" has been reduced to 9 inches, and the largest ensigns are not more than 22 breadths, but the relative length of the flag has been slightly increased. Thus the largest ensign of 1742 was 51 feet long and 28 feet deep; the largest modern ensign is 33 feet long and 16½ feet deep. The largest Union flag is now 18 breadths, i.e. 27 feet by 13 feet 6 inches, while pendants vary from 3 to 20 yards in length. The proportions of the crosses in a modern Union flag are as follows:
| St George's Cross | { red | 1/5 of width of flag |
| { white border | 1/15 " " | |
| St Andrew's Cross | white | 1/10 " " |
| { red | 1/15 " " | |
| St Patrick's Cross | { white border | 1/30 " " |
It may be observed that the white "fimbriation" of the St Patrick's cross, required by the rules of heraldry to prevent the colour red from touching the colour blue (white being a "metal": silver) is now taken from the width of the red, reducing that from 1/10 to 1/15. The two crosses, St Andrew's and St Patrick's ought, however, to be of equal width, and the fimbriation of the latter should therefore be taken from the blue ground.
In the white ensign the St George's cross in the fly is 2/15 of the width of the flag. In the red and blue ensigns the Union canton now occupies one-fourth of the flag; in the white it is, of course, slightly smaller owing to the space occupied by the large St George's cross.
The pendant at the masthead of one of H.M. ships is a sign that the ship is in "commission"; that is, in active service under the command of an officer of the Royal Navy holding a commission from the Crown or the Lord High Admiral or the Commissioners for executing that office. It is not flown in ships in reserve. In ships flying the flag of an Admiral, or a Commodore's broad pendant, the Admiral's or Commodore's flag is in itself sufficient indication that the ship is in commission, and the pendant is not flown in those ships. It is, however, not struck when a captain hoists a Senior Officer's pendant.
It is difficult to say when the custom of hoisting a pendant on commissioning the ship became established. Mainwaring, writing about 1623, speaks of the pendants as serving solely "for a show to beautify the ship," and Boteler, ten years later, knew them only as used for this purpose or as a means of distinguishing the squadrons of a fleet[413]; but from 1661 onwards there was, in addition to the three squadronal pendants with red, white or blue fly, a fourth with the fly striped red, white and blue. This was the distinctive pendant of all H.M. ships in commission which did not form part of a fleet divided into squadrons by the red, white and blue squadronal colours.
The first step towards the recognition of the pendant as the distinctive sign of a man-of-war was taken by the Proclamation of 1661, which assigned the Union pendant to H.M. ships only, and the next by the Proclamation of 1674, which forbade merchantmen to fly any pendant whatsoever; but although the use of a pendant was thereby confined to men-of-war, it does not seem to have been the custom at that time to fly it continuously. It is clear from the Diary which Teonge, the naval chaplain, kept during his service in the Navy from 1675 to 1679, that the pendant was only hoisted—with the jack and ensign—when the ship wished to make her nationality known; or was preparing to fight; or on days of rejoicing, when pendants were hung from every yardarm; but the significance of the pendant seems to have been generally recognised at that date, for in the account which he gives of the launching in 1676 of a brigantine by the Knights of Malta, he says that after the religious ceremony, "they hoysted a pendent to signify shee was a man of warre, and then at once thrust her into the water."
Although it was not until 1824 that the King's Regulations for the Navy contained any instruction that ships in commission were to fly a pendant, it is probable that the practice of flying a pendant continuously in H.M. ships in commission was established about the end of the seventeenth century, for the first edition of the Regulations (1731) contained a direction to Captains "to husband the Ship's Colours, and not to keep them abroad in windy weather, the Pendant being a sufficient mark of distinction," from which it is clear that the latter was then flown continuously. The practice in the Navy at the beginning of the nineteenth century is given by Captain Basil Hall[414] in the following words:
In the mean time I must proceed to put my ship in commission. The first thing to do is to get hold of one of the warrant-officers to "hoist the pendant," which is a long slender streamer, having a St George's cross on a white field in the upper part next the mast, with a fly, or tail, either Red, White, and Blue, or entirely of the colour of the particular ensign worn by the ship; which, again, is determined by the colour of the Admiral's flag under whose orders she is placed. The pendant being hoisted shows that the ship is in commission, and this part of the colours is never hauled down day or night. At sunset, when the ensign is hauled down, a smaller pendant three or four yards in length, is substituted for the long one, which, in dandified ships, waves far over the stern. Ships in ordinary[415] hoist merely an ensign.