Some say he wrote the final draft under the table, some say dialogue polish, some say script polish, some say earlier drafts..but the consensus is that Mankewicz had involvement on both TSWLM and MR, both credited to Christopher Wood.
The TSWLM drafts are numerous and all over the place. They'd make a fun read if ever found. Best would be the too topical Maibaum draft that opened with S.P.E.C.T.R.E. gunned down by terrorists who then steal a nuclear sub to destroy Middle Eastern oil fields.
But my question is how much input do you think Tom Mankewicz had on the Spy script? Some one liners sound like him, but overall you can feel the input of a new writer (Wood) on both films, and after reading his outstanding TSWLM novel, one who is also having to please Broccoli and the public.