It was estimated that an additional twenty-five to thirty ocean escorts and eleven destroyers would be needed to include the above trade in convoy.
The Mediterranean trade is dealt with later.
The question of speed was naturally one of great importance in the convoy system.

As has been stated earlier, the speed of a convoy like that of a squadron or fleet is necessarily that of the slowest ship, and in order to prevent delay to shipping, which was equivalent to serious loss of its carrying power, it was very necessary that convoys should be composed of ships of approximately the same speed.

In order to achieve this careful organization was needed, and the matter was not made easier by the uncertainty that frequently prevailed as to the actual sea speed of particular merchant ships.

Some masters, no doubt from legitimate pride in their vessels, credited them with speeds in excess of those actually attained.

Frequently coal of poor quality or the fact that a ship had a dirty bottom reduced her speed to a very appreciable extent, and convoy commodores had occasionally to direct ships under such conditions to drop out of the convoy altogether and make their passage alone.