I knew I'd seen a painting of this in my dim and distant pass:
Friendly Ordnance by Ronald Wong.
Factory Fresh Spitfire Mk IXe's make their way to the forward airfields of Normandy carrying kegs of beer. The English brewery of Heneger and Constable donated fresh beer for the troops fighting in Normandy, and someone (history does not record who) came up with the idea of strapping the beer kegs to the underwings of the Spitfires that were being shipped to the forward airfields. The troops loved the freshly delivered, cold beer, but as with all good things, the British Ministry of Revenue and Excise stepped in and notified the brewery that it was in violation of the law in that it was exporting beer without paying the taxes on it. Needless to say, this morale raising gesture was shortly terminated.