I believe that Wadi Halfa, on the banks of the Nile but in the middle of nowhere, was (and still is) at the end of one of the few railways in Sudan, and therefore bulk fuel could be brought in by tanker railcar from Port Sudan on the Red Sea. It started as a stop for fuelling on the Imperial Airways pre-war flying boat African service between Cairo and Khartoum, landing on the Nile itself (so no paved runway issue then !). It will be interesting to find if the old airfield was alongside the flying boat base.