They didn't actually copy the jeep, which is why a landy don't look same as a Willys. What they did do was measure a jeep chassis all over before, err............designing theirs!
The design for the original Land Rover vehicle was started in 1947 by Maurice Wilks, chief designer at the Rover Company, on his farm in Newborough, Anglesey.[12] It is said that he was inspired by an American World War II Jeep that he used one summer at his holiday home in Wales.[13][14] The first Land Rover prototype, later nicknamed 'Centre Steer', was built on a Jeep chassis and axles