I would say around the time of the Crimean War is when wooden ships started to become old. The Royal Navy possessed many ironclads from the 1860s-1880s. The Royal Navy rarely used ironclads in major combat. The problem was that during the ironclad period Britain was in no major combat. The Royal Navy didn't participate in any "modern" navy until WW1. The Royal Navy was the largest of its time and wasn't truly "modernized until" the 1870s or 1880s. The Royal Navy had a big competitor in Imperial Germany. For a time from about the 1880s-1940s Germany was pushing for industrialization to compete with England. The main reason for modernization of the Royal Navy was keeping its naval superiority and colonial empire as well as competition with Germany.