Definitely Brian Cant, and Fred Harris, and Floella Benjamin !
...John, Val, and Pete - The Goodies (I still think they're young enough to make a comeback)...etc etc
thenry, 'national treasure' means someone who is alive, but, even alive, Abraham Lincoln would not be one. He is a revered figure now but too controversial in life to be loved by all. Being non-controversial is a key element of being a 'national treasure'. Even Churchill might not qualify; I can't think of any politician, past or present, who would.
fred is right, it isnt just people you remember and are fond of - brian cant, floella etc although kids loved them, but theyre relatively unknown now so dont qualify
Grade I: persons of exceptional interest,
Grade II*: particularly important persons of more than special interest.
Grade II: persons that are of special interest, warranting every effort to preserve them