After the Japanese formal surrender in September, Implacable ferried Allied troops and prisoners of war back to Australia and Canada for the rest of the year.

The initial change was to increase the carriers' speed to no less than 32 knots (59 km/h; 37 mph) which required the addition of a fourth steam turbine and associated propeller shaft.

[6] The turbines were designed to produce a total of 148,000 shaft horsepower (110,000 kW), enough to give them a maximum speed of 32.5 knots (60.2 km/h; 37.4 mph).

The Implacable class carried a maximum of 4,690–4,810 long tons (4,770–4,890 t) of fuel oil which gave them a range of 6,720–6,900 nautical miles (12,450–12,780 km; 7,730–7,940 mi) at 20 knots (37 km/h; 23 mph).

The carriers were fitted with nine arrestor cables aft that were designed to stop landing, at speeds of up to 60 knots (110 km/h; 69 mph).

In case of damage to the rear flight deck, the Implacable-class ships also mounted three additional forward arrestor cables to permit aircraft to land over the bow.

[9] Both hangars had a height of only 14 feet which precluded storage of Lend-Lease Vought F4U Corsair fighters as well as many post-war aircraft and helicopters.

The crewmen, maintenance personnel and facilities needed to support these additional aircraft were housed in the lower hangar.

[14] The two ships were also fitted with approximately sixty Oerlikon 20 mm autocannon in varying numbers of single and twin-gun mounts.

The Controller of the Navy asked if the time and cost of the reconstruction could be reduced, but the minimum modifications were the most expensive as they involved structural alterations.

In order to reduce the amount of structural work, the requirement to replace the boilers was cancelled and the ship would receive existing radars instead of systems then still under development.

Five months later the Admiralty decided that Victorious would be the last fleet carrier modernised as experience showed that the process would take longer and cost more than was practicable.

While under construction, the ships had their forward lift enlarged to take non-folding aircraft like the Hawker Sea Hurricane and the early models of the Supermarine Seafire, the flight deck was widened abreast the forward lift, splinter protection was added as were seven diesel generators, each in their own watertight compartment.

[19] Implacable's construction was suspended in 1940 in favour of escorts needed in the Battle of the Atlantic so that the two carriers were launched within days of each other.

She embarked portions of her air wing for training in late August and was assigned to the Home Fleet on 7 October at Scapa Flow after working up.

She joined ships searching for Tirpitz a week later and some of her Fairey Fireflies spotted the battleship off Håkøya Island near Tromsø.

[28] In late October, the carrier's Seafires arrived and she participated in Operation Athletic off the Norwegian coast, sinking four warships and two merchant ships and damaging a German submarine.

[29] In November and December, Implacable provided air cover for minelaying operations and attacked German shipping off the Norwegian coast.

On 15 December she began a refit at Rosyth preparatory to her transfer to the BPF, which included augmenting her light AA armament.

She arrived at Sydney on 24 August and spent most of the rest of the year ferrying Allied prisoners of war and soldiers back to Australia and Canada.

[32] While Indefatigable was still conducting builder's trials,[33] a de Havilland Mosquito landed aboard on 25 March 1944, piloted by Lieutenant Eric Brown.

[34] After working up the ship was assigned to the Home Fleet in early July 1944 with an air group of Seafires, Fireflies and Barracudas.

She was also assigned to a series of attacks on Tirpitz, Operation Goodwood, in late August which failed to significantly damage the battleship.

During these operations, Indefatigable became the first British carrier to be hit by a kamikaze when one penetrated the combat air patrol (CAP) and struck the base of her island on 1 April.

After Okinawa had been secured, the BPF arrived back at Sydney on 7 June and Indefatigable was delayed rejoining operations as she required repairs to her machinery.

After the ceasefire, her aircraft continued to fly CAP and flew reconnaissance missions looking for Allied prisoners of war.