[1] However, the training and seamanship of the crews, especially with regards to navigation, and the fact that these boats were hard pressed to make 10 kn (12 mph; 19 km/h), meant that the MCS at this time was only capable of inshore rescue operations.

The work of the BPBC would lead in the late 1930s to the RAF 100 class High Speed Launch (HSL), based on the elongated hull of a 64 ft (20 m) Motor Torpedo Boat the RAF 100 was designed to have a maximum speed of 35 knots (40 mph; 65 km/h), and achieved over 39 knots (45 mph; 72 km/h) during trials, making it one of the fastest boats of the time.

[1][2] However, the internal arrangements of the RAF 100 was to prove vulnerable to combat damage, its high deck made the recovery of aircrew in the water difficult, and for wartime use it was underarmed.

During the Battle of Britain the MCS could only keep 10 of 13 HSL launches available for air-sea rescue operations at any one time and the high performance of the craft was brought at the expense of engines which had a service life of only 360 hours.

[3] Even with the help of civilian vessels and the Royal Navy, aircrew who baled out or ditched in the North Sea and English Channel had only a 20% chance of being returned to their squadrons.

The air-sea rescue squadrons of the ASRS flew a variety of aircraft, usually hand-me-downs rejected or withdrawn from front-line service by the RAF's other branches or, as in the case of the Walrus, begged from the Navy.

[3] They used Supermarine Spitfires and Boulton Paul Defiants to patrol for downed aircrew and Avro Ansons to drop supplies and dinghies.

[6] In addition to more and better "whalebacks", the ASRUs would acquire United States built powerboats under Lend-Lease, known as "Miamis" in RAF service, from the name of their builder.

The MCS craft also became much better armed, sporting multiple machine guns in powered turrets derived from those found in the RAF's multiengined bombers.

As the British withdrew from Empire, and aircraft reliability improved, the need for rescue craft to provide cover for the routes that the troop planes and supply transports flew waned, and with the withdrawal from service of flying boats a large part of the Branch's reason to exist disappeared.

Physically isolated from the majority of RAF bases and personnel, with the withdrawal of the flying boats and the absorption of Coastal Command into Strike Command, the majority of RAF bases were now inland: the Marine Branch becoming largely forgotten and neglected by the rest of the Royal Air Force.

HMAFV Stirling (4002),[7] a Spitfire Class Rescue Target Towing Launch Mk.III,[8] and its crew were used for the filming of the Secret Army TV drama series episode Prisoner of War in 1978.

In 1986, the Marine Branch was disbanded, the last of the RAF's vessels retired and handed over to civilian contractors for the target towing role.