Converting "Campbeltown" for the raid took ten days. She had to be lightened to raise her draught to get over the sand banks in the estuary. This was achieved by completely stripping all her internal compartments. The dockyard removed her three guns, torpedoes and depth charges from the deck and replaced the forward gun with a light quick-firing 12-pounder gun. Eight 20 mm Oerlikons were installed on mountings raised above deck level. The bridge and wheelhouse were given extra armour-plate protection, and two rows of armour were fixed along the sides of the ship to protect the commandos on the open deck.