Well then; it has been a few years but a DC-10-30 will always be able to make London to Los Angeles with a full payload.
With CF6-50C2B engines and (speaking as a completely ballpark figure) if you allowed 18,000 lbs (9 tonnes) per hour fuel burn for the the total flight, then that figure would cover everything including contingency and diversion fuel.
So, the immediate burn after take off might be 10 tonnes per hour but 10 hours later ( 4.5 hours after an L1011 would have had to land for fuel) the fuel burn would be down to around 7 - 7.5 tonnes per hour.
Therefore, for a 10 hour flight, the fuel loaded would be somewhere around 90tonnes and that would include all of the above contingencies.
First find a decent DC-10-30F!