The Old Man on the Pole was a prophet who lived on the planet Hawalius, and spent all of spring, summer and autumn sitting on top of a succession of poles, and had been doing so for the past forty years. In winter, however, he went south and sat on the chimney of a beach hut. He advised Arthur to buy a beach hut.
When Arthur Dent went to talk to him in Mostly Harmless/the Quintessential Phase, the Old Man confused him by moving to different poles without appearing to climb down the poles or indeed move a muscle. He was scornful of Arthur, but agreed to give him a prayer tailored to his individual needs. He was also scornful about the Old Woman in the Cave, saying that the only reason he got the beach hut was that she had turned it down.