List of things the Swallows, Amazons and others did which you should probably never do without asking your parents or great-aunts first:
free soloing 40 feet up the limbless trunk of a very tall pine tree, the lighthouse tree (SA17). John also goes up a tall old ash at Camp Might Have Been (PP9).
But at the end of Swallowdale Captain Flint climbs the tree on Wild Cat Island. They see the lantern hanging from the tree; and decide someone has taken the trouble to climb those thirty feet of smooth trunk to hang a rope over the bough .... , and think that someone else has occupied the island. But when they charge the camp, and find their own tents there and Captain Flint asleep, he says Hot work, you know, shifting all those things down to the launch, and that tree takes some climbing (SD36).