The extension to Aldersgate Street and Moorgate Street (now Barbican and Moorgate) opened on 23 December 1865, and all four lines were open on 1 March 1866. The parallel tracks from King's Cross to Farringdon, first used by a GNR freight train on 27 January 1868, entered a second Clerkenwell tunnel before dropping at a gradient of 1 in 100, passing under the Ray Street Gridiron carrying the original Met track before ascending a 1 in 40 slope to Farringdon. A plan was developed to extend the City Widened Lines to Euston, but this was aborted and never completed.