It's all in the name

We travelled down to Abergavenny for the British Prienteering Championships being held this weekend in the Forest of Dean. We stopped at Tebay Services for a picnic and I spotted this van just before it pulled away. It's not a great blip, but I was intrigued behind the psychology of the name Grumpy Mule. It's quite good but doesn't seem to say coffee to me.