He held this position for three years before leaving to enter the Imperial College of Science in London to start a PhD degree.
[1] As a result of his lifelong interest in bushwalking, Bratt joined the Imperial College Exploring Society Karakorum Expedition conducted in 1957–58, the aim of which was to scale the world's second-highest mountain peak.
As a member of the British Glaciological Society he accepted an invitation from Eric Shipton to join an expedition to Patagonia in 1958–59.
After returning to Australia, he set up a herbarium in his home in West Moonah, and added many lichens to his collections from numerous bushwalking trips in Tasmania.
After suffering kidney failure in 1974, he had to forgo major expeditions, but he was able to spend more time with the specimens in his herbarium, and most of his lichen publications were published after that.