In December 1953 the Nissan Motor Co. signed a "technological co-operation agreement" with the Austin Motor Co. Ltd. of Great Britain. The result of this agreement gave Nissan the rights to build and market the Austin A40, and later the Austin A50, in Japan. It also let them use the Austin engines and chassis as a basis for other vehicles such as the Nissan Junior B40. The agreement expired in March 1960, but Nissan made the most of those intervening years, to the point where the next generation of Nissan engines were close to being a blatant copy of the Austin A and B series engines. Austin were considering taking legal action against Nissan at the close of the agreement, but were convinced by the US government, who still had post-war occupying forces in Japan assisting with re-building the country after the war, not to persue the matter. Japan was only a minor player in the car industry, and Nissan held no threat to the might of Austin, or so they thought. Austin should have been more worried, a mere 10 years later Nissan had become one of the largest car manufacturers in the world, and Austin was dead in the water.
But to call the Nissan engines built after the Austin agreement a blatant copy would be to sell them considerably short. Yes they were based heavily on the Austin designs, but they also made significant changes to the designs. The Nissan engines were built with a degree of engineering precision the British couldn't come close to matching. The British engines were notoriously oil leakers (the old standard joke was Q/ how do you tell if an Austin needs oil A/ it's stopped leaking ) , but even 40+ years down the track old Nissan engines just don't leak oil. The other thing the did was significantly improve the cylinder head and manifold design, Nissan engines all produce more power than their Austin equals. (for example 1965 Fairlady 1600 = 96hp, 1965 MGB 1800 = 95hp, or 1966 Datsun Bluebird SS 1299 = 77hp, 1966 Austin Healey Sprite 1275 = 48hp etc.) The other thing Nissan had that Austin lacked was reliability, the Austin engines weren't bad mind you, it's just that the Nissan versions were practically indestructible. The biggest impact Nissan made on overall vehicle reliability was it's use of Japanese made electrical components. Nissan's electrical component suppliers such as Hitachi, EverWing, Mitsubishi Electrical, Niles and Myamoto supplied 100% reliable and totally dependable parts, Austin has Lucas. ( http://www.hermit.cc/mania/tmc/articles/lucas.htm) 

AUSTIN  A40  by  NISSAN 
(1954 Model)

Powered by a Nissan built version of the Austin 1200cc 42hp OHV 4cyl engine.

AUSTIN  A50  by  NISSAN 
(1955-1957 Model)
 

Powered by a Nissan built version of the Austin 1500cc 57hp OHV 4cyl engine.

AUSTIN  A50  by  NISSAN 
(1957-1959 Model)

Powered by a Nissan built version of the Austin 1500cc 57hp OHV 4cyl engine. These later cars started to show some very Japanese features, such as the twin mirrors mounted right up the front of the car and the bright orange fog lights.

CUTIE FACT - Nissan weren't the only ones building other people's cars. Nissan weren't the only Japanese manufacturer to have a "technological co-operation agreement" with another European car maker. Hino built Renaults under licence in the late 1950s/early 1960s, and Isuzu built the Hillman Minx in the late 1950s. In 1917 the company that would later become Isuzu were building Wolesleys under licence. Before the Second World War Nissan also held the rights to build the American designed Graham Paige cars, which were sold as the Nissan 70. In the 1980s Nissan held the rights to build and market the Volkswagen Santana in Japan.