 Up to the early 1930s , camping by Boy Scouts continued on Brownsea Island . In 1963 , a formal 50 @-@ acre ( 200 @,@ 000 m2 ) Scout campsite was opened by Olave Baden @-@ Powell , when the island became a nature conservation area owned by the National Trust . In 1973 , a Scout Jamboree was held on the island with 600 Scouts . 
