Part of the problem is that the Pumping station that moves the fuel was beside the depot that exploded and has apparently been damaged. This will also prevent Shell/BP pumping various fuels to/from their yard which was slightly further away from the one that exploded and recieved less damage.

I don’t know for certain but I wouldn’t be surprised if somewhere like Heathrow may use in excess of 10 million litres of fuel a day, and if you take say a third of that away, it becomes a logistical nightmare to tanker in say 3 million plus litres which would be up to 120 truck loads, so as Skymonster suggests this may go on for a while until they find another way. Reducing demand by up to a third by applying uplift restrictions is part of this