In Berlin the German press campaign against Poland has been suddenly intensified, and it is scarcely a coincidence that this has happened precisely at the moment when Franco's victory has increased the prestige of the Rome-Berlin axis.
In regards to that:
On the evening of March 30, [British Ambassador in Warsaw Sir Howard] Kennard presented to [Polish Foreign Minister] Beck an Anglo-French proposal for mutual-assistance pacts in case of German aggression. But even this step was overtaken by events. Fresh reports of the possibility of an imminent German attack on Poland prompted the British government on the same evening to ask Beck whether he had any objection to an interim unilateral British guarantee of Poland’s independence. Chamberlain had to know by the morrow, as he wished to answer a parliamentary question on the subject. Beck - his sense of relief may be imagined - had no objection. In fact, he told Kennard, he “agreed without hesitation.”
William L. Shirer, The Rise and Fall of the Third Reich
3/30/39 update at #6.