I'll admit I had to google what this is called even though I've seen it many, many times. Initial results all said harbour cleat but this sounds too American to me, so I'm going with the other search result of harbour bollard, which sounds much more plausible in Ireland. Still, please let me know if I'm wrong on this. I'd been looking for something all week for the rust theme and this caught my attention...
Nice shot Paul. I think bollard sounds good. When I think of a cleat I visualize a kind of "T" shaped piece of metal bolted down to the dock and this doesn't look anything like that.