If one adjective could describe renowned British broadcaster, naturalist and author Sir David Attenborough, it would be "indefatigable."   Though having physically slowed down with age, the now 100-year-old presenter's passion for the natural world — and his enthusiasm in sharing it with viewers — has not waned.  He holds the Guinness World Record for "the longest career as a television presenter and naturalist." From his on‑screen debut in "Animal Disguises" in 1953 to the recent  Netflix