 
 <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. <hau> Wannan shine bayanin da ya dace: London Underground ya fara buɗewa a matsayin "hanyar jirgin ƙasa" a cikin 1863 kuma an buɗe layin farko na lantarki a ƙarƙashin ƙasa a cikin 1890, yana mai da shi tsarin metro na farko a duniya. Saboda haka, amsar karshe ita ce 1890. 