Complex sentence: The Sheffield, Ashton-under-Lyne and Manchester Railway had opened between Manchester and Sheffield in 1845, but as early as 1844 the promoters of the Sheffield and Lincolnshire Junction had approached the SA&MR with a view to the latter leasing it.
Split into simpler sentences: The Sheffield, Ashton-under-Lyne and Manchester Railway had been opened in 1845 between Manchester and Sheffield. As early as 1844 the promoters of the Sheffield and Lincolnshire Junction Railway had approached the SA&MR with a view to the latter leasing it.