There were more than 200 convoy routes
in existence during the war of which 94 routes were under attack
by U-boats. Each convoy was known by two or more letters designating
the route and a consecutive number added in chronological order.
Additionally, the letter 'F' was sometimes used to identify fast
convoys (9 knots) and 'S' for slow ones (7 knots). The
convoys received the number when they left harbour. Vessels
that could make 13 knots or more could qualify for independent sailing
but the losses amongst this group were three times higher than for
those travelling in convoy.
There are two sources of published information:-