Jim Olsen is a British engineer who worked in the Middle East and North Africa before retiring to settle on La Palma in 1962. A site testing campaign was carried out at Fuente Nueva during 1975 and 1976 for what would eventually become the Observatorio del Roque de los Muchachos by small teams of two or three people at a time drawn from a number of different countries, coordinated by the Royal Observatory Edinburgh. On the British side, the campaign was part of a search for a site for a new observatory, then referred to as the Northern Hemisphere Observatory. There was then no road up the mountain and so the site testers had first to drive up in a Land Rover for about an hour from Los Llanos and then walk for another two hours to the top. Supplies and equipment were carried on mules.

In Los Llanos the teams stayed with Mr Jim and Mrs Beverly Olsen. Jim was a retired oil engineer and Beverly Olsen was a schoolteacher. Jim Olsen took a great interest in the project and made tape recordings of the various members of the teams between 1974-1976.