It has come to my attention that the editor of Harvey is after all human. Consider the following situation.
Claimant suffers a very serious act of sexual harassment on June 1st. Having thought about the matter she resigns on July 1st claiming constructive discriminatory dismissal. But she does not submit her ET1 till September 28th.
The question is that of when time began to run. If from the last act of discrimination then the claim is out of time. If it runs from the moment of resignation then the claim is clearly in time.
Harvey tells us that there are two conflicting decisions of Employment Appeal Tribunal on the point: In Derby Specialist Fabrication Ltd v Burton  IRLR 69 Keene J held that time runs from the date of resignation. In Commissioner for the MPC v. Harley  263, Charles J says that it runs from the date of termination. Harvey goes on to say that the issue needs to be resolved by the Court of Appeal (P1 (1) F 112).
However the issue has in fact already been resolved by the Court of Appeal. The issue is whether dismissal, a listed detriment under the discrimination legislation, (see now Equality Act S. 39 (2) (c)) includes constructive dismissal. If it does it is very difficult so see how a constructive dismissal could be said to have occur prior to resignation. Precisely this point arose before the Court of Appeal in Meikle v Notts City Council  IRLR 703 in which Keene LJ was quite clear that time ran from the moment the employee resigned (though quare the case where the employee resigns on notice which does not appear to be covered by Meikle).
Thus notwithstanding Harvey the position is clear: its authors are not after all infallible.