 
 <translate> This is the relevant information: The London Underground first opened as an "underground railway" in 1863 and its first electrified underground line opened in 1890, making it the world's first metro system.
So, the final answer is 1890. <ibo> Nke a bụ ozi dị mkpa: London Underground meghere nke mbụ ya dị ka "ụgbọ okporo ígwè dị n'okpuru ala" na 1863 na ụzọ ụgbọ oloko mbụ ya nke nwere ọkụ eletrik meghere na 1890, na-eme ka ọ bụrụ usoro ụgbọ oloko mbụ n'ụwa. Ya mere, azịza ikpeazụ bụ 1890. 