There is a recent publication on the Jap raids on Darwin that is worth a read. Last I heard was being edited to improve the text but it is the info that makes it worth reading anyway.
Raid could have be intercepted but the most senior officer threatened the intelligence officer with a court martial if he bought any more ludicrous claims that the Japs were capable of an attack on Darwin. Not even Pearl Harbor and Singapore were capable of waking this genius (yet the RAAF still consider him a great leader!!!!!!).
Good photos and obviously read the Royal Commission Inquiry on the raids.
Japanese Blitz On Darwin by John Thompson-Gray,