after 2 February 1970
estimated · probable · preferred
Why
No further precision than 'recently' after the death is available; the lecture also garbles Russell's 90th-birthday anecdote (actually May 1962) together with the death account, but the death reference is the dating anchor.
Reasoning
Bertrand Russell died 2 February 1970, historically documented; Neville treats it as recent news, dating delivery to shortly after that date. This matches the lecture's own already-established certain year-1970 delivery claim (d2, internal_or_header_evidence) and is inconsistent with both catalogue claims (1957, 1968-05-10), neither of which is disturbed here.