 The island was reopened to the public in 1963 by Lady Baden @-@ Powell when it came under the control of the National Trust . She planted a mulberry tree to mark the occasion . The Trust has continuously maintained the island since then as a conservation area . In 1964 , 50 acres ( 200 @,@ 000 m2 ) near the original campsite were set aside for Scout and Guide camping . In 1973 , a Jamboree was held on the island for 600 Scouts from seven nations , along with one of the original campers , then aged 81 . 
