Smalls Lighthouse is a lighthouse that stands on the largest of a group of wave-washed basalt and dolerite rocks known as The Smalls approximately 20 miles west of Marloes Peninsula in Pembrokeshire, Wales, and 8 miles west of Grassholm. It was erected in 1861 by engineer James Douglass to replace a previous lighthouse which had been er…Smalls Lighthouse is a lighthouse that stands on the largest of a group of wave-washed basalt and dolerite rocks known as The Smalls approximately 20 miles west of Marloes Peninsula in Pembrokeshire, Wales, and 8 miles west of Grassholm. It was erected in 1861 by engineer James Douglass to replace a previous lighthouse which had been erected in 1776 on the same rock. It is the most remote lighthouse operated by Trinity House.