The wooden Mark I and Mark II hulls suffered in mediterranean and tropical climates so an alloy hull was designed. The Mark III was to be fitted to Shackletons, much larger than the Warwick which enabled them to be larger. Although fifty hulls were produced they were not used operationally..Mark III
Airborne Lifeboat fitted with purpose designed HRD twin cylinder engine. The lifeboats were of all-aluminium construction with bright yellow hulls and blue front and aft dodger covers. They were deployed from modified Shackleton aircraft on two parachutes at a rate of 20 ft per second. They had grab rails along the hull just above the waterline and a fold down hatch centrally located on both sides to allow survivors to easily crawl into the lifeboat. A number of these craft were sold out of service and became a familiar sight around the British coast for many years.