At the start of the second chapter of Dr No, M is arriving at the office on a cold, raw March 1st (1956) in London. He exits his car, and speaks to his chauffeur:
‘Won’t be needing the car again today, Smith. Take it away and go home. I’ll use the tube this evening. No weather for driving a car. Worse than one of those PQ Convoys.’
This is about as close as M gets to using humor. He is referring to the Arctic convoys of World War II – an operation where Allied ships brought supplies to the Soviet Union.
These convoys often met with severe weather on their trips, as well as German opposition.
The above photograph is from one of those convoy missions and likely shows what M had in mind when making the reference.