"Whatever else history may or may not say about these terrible,
tremendous years, we can be sure that Neville Chamberlain acted with
perfect sincerity according to his lights and strove to the utmost of
his capacity and authority, which were powerful, to save the world from
the awful, devastating struggle in which we are now engaged. This alone
will stand him in good stead as far as what is called the verdict of
history is concerned."
History has the benefit of hindsight, which is something Chamberlain was not privy to. The entirety of Churchill's eulogy can be read here.