Chamberlain has gotten a bum rap from history - he did not think that appeasing Hitler was anything other than a temporary expedient to buy time. The British government at the time (not just Neville himself) felt that Germany’s modern air force was powerful enough to destroy them on its own and that they couldn’t challenge Hitler until they had enough modern fighters (Hurricanes and Spitfires) to defend themselves. In additional fact, the only reason Britain had these fighters in the pipeline at all was because Chamberlain had resisted the entreaties of Britain’s own “bomber mafia”, a group of RAF officers and industrialists who wanted Britain to build their own massive bomber fleet for offensive action in lieu of defensive fighters.
In retrospect, the impact of the bomber was vastly overestimated in the 1930s, as evidenced by the fact that Germany ended up suffering a much more massive assault at the hands of British and American bomber fleets later in the war while continuing to increase military production all the while. Britain under Chamberlain should have stood up to Hitler much earlier, but this was an error of judgement and not an act of capitulation.
TBF he never specified which day.