If I remember correctly, the report is quite interesting in that the investigators 'hinted' that although the crew must bear primary responsibility for failing to ensure adequate fuel was carried on the flight, perhaps little or no fuel had actually been pumped aboard the aircraft from Santander on the final leg despite the F/O checking the bowser reading and signing for an adequate amount.
The investigators used data from the previous couple of flights which were also Exeter->Santander->Exeter and similarly loaded, extrapolated rate of climb data from a plot of time/altitude from the FDR and found that on departure of the accident flight the Viscount was probably considerably lighter to the tune of approximately the weight of fuel that should have been uploaded. Additionally, they calculated (hypothetically.....) that if no fuel had actually been uploaded, the time at which the flight would run out using the previous flights as models for climb/cruise altitude etc. That time came to with 3 minutes of the actual time the aircraft did run out...........