I'm not sure if it's the main fuel bowser but it is probably no.2 in the fleet. I think it's the Avgas tanker while a larger fuel truck fuels the Jet A1 birds but I'm not 100% sure on that. It seems appropriate that that fuel trailer is being towed around by something agricultural! It probably helps when the call comes to fuel up a plane parked on the grass after a couple of days of Irish weather.
500 Fan.