The starting point would be to have someone check the charcoal canister. Nothing unique to Bentley. Frequently overfilled or toped off gas tank causes this problem . What happens is the excess gas back flows into the anti-pollution device called a charcoal canister and contaminates the charcoal causing the venting system on the gas tank to not work properly. This condition results in an impossibly slow gas fill situation. If this is not the case the next step is to check the purge valve to make sure that it is open when filling. Regrettably chasing down a slow fill situation is not straightforward.

Also, the possibility of a plugged fuel fill tube is unlikely. This can happen if the car is damaged underneath or in an accident. However, it's worth a quick check. Someone with an inspection camera can quickly diagnose that one.