The OB series of convoy sailed from Liverpool and catered for vessels sailing transatlantic to North and South America; for the South Atlantic to Freetown, the Cape and beyond together with coastal traffic. En route, vessels sailing from the Bristol Channel ports (Avonmouth, Barry, Newport and Cardiff) would join the convoy at a designated position, usually a few miles south of the Smalls Lighthouse (51.43N, 5.40W). The convoy was initially routed south through St. Georges Channel (see here) and then west to be dispersed after dark in position around 50N, 26W (about 750 nautical miles west of Lands End). Later, when bases in France were available to the Axis, the convoy was routed round the north of Ireland. At intervals, the OB series was designated with the letter 'G' and would be combined with the OA series (also designated 'G') for direct passage to Gibraltar or 'GF' to denote a fast convoy. The combined convoy was then coded as the OG series (see here). The complimentary OA series of the same number sailed on the same date from Southend and later from Methil (from July 13, 1940). In addition to their conjunction in the OG convoys, the OA and OB series would combine if they met each other at sea. The OA series also carried a lot of local traffic from the Thames to the south coast ports of Southampton, Poole, Plymouth (Devonport), Fowey, Falmouth etc.
The OB series ran from September 7, 1939 (OB.1) to July 21, 1941 (OB.349) when two new convoy series were formed. The OS series to Freetown, Sierra Leone, for ships bound for the South Atlantic (later sailing with the KMS series to Gibraltar) and the ON series sailing west to Halifax although initially these were still dispersed before reaching their destination. The OA series ceased on October 24, 1940 (OA.234).
See also the entry for OB convoys in the Arnold Hague database.
The author wishes to express thanks to Dominique Lemaire and Donald Bertke for diligently proofreading these convoy pages.