This brilliant yellow lichen is growing on the rocks at Corrachadh Mor, the most westerly point on the British mainland, just south of Ardnamurchan Point lighthouse.
It seems to grow on the sides of the rocks which are downwind of the prevailing westerlies.
The lichen is called golden shield lichen, Xanthoria parietina, and, in the close-up that's possible with a digital camera, it's quite beautiful. Lichens are complex composite organisms consisting of a fungus which hosts a photosynthetic partner, usually a green alga or a cyanobacterium, so the two grow together in a symbiotic relationship. It requires nitrogen to thrive, this apparently provided by the local seabirds.
Golden shield lichen seems to be able to grow in the most exposed places battered by winter gales and sea spray, but only a little further inland it's joined by another lichen. The Diary tried very hard to identify this one but failed.