Efforts were made to disperse production and to employ the use of shadow factories to minimise the damage caused by "Luftwaffe" bombing raids. Major sub-assemblies for the Swordfish were produced by four subcontractors based in neighbouring Leeds, these were transported by land to Sherburn for final assembly. Initial deliveries from Sherburn were completed to the Swordfish I standard; from 1943 onwards, the improved "Swordfish II" and "Swordfish III" marks came into production and superseded the original model. The Swordfish II carried ASV Mk. II radar and featured metal undersurfaces to the lower wings to allow the carriage of 3-inch rockets, later-built models also adopted the more powerful Pegasus XXX engine. The Swordfish III was fitted with centimetric ASV Mk.XI radar between the undercarriage legs, deleting the ability to carry torpedoes and retained the Pegasus XXX powerplant.