The story
Founded by London, Chatham and Dover Railway and South Eastern Railway on Jan 1, 1899.1
By the end of the 19th century, the SER and LC&DR had fought over a small and not particularly lucrative territory for 40 years. Both were notorious for the poor punctuality of their services and the decrepitude of their rolling stock, and the struggles had driven both companies to the verge of bankruptcy. It became inevitable that they must combine or succumb.
The SE&CR was formed on 1 January 1899, when the SER and LC&DR formed a "management committee" comprising the directors of both companies. This merged the two companies' operations, although they remained legally separate, with receipts split 59% to SER and 41% LC&DR until the Grouping, to avoid the costs and risks of a formal merger.
On 5 August 1899 the South Eastern and London, Chatham and Dover Railways Act 1899 (62 & 63 Vict. c. clxviii) was passed.
From Wikipedia’s article on South Eastern and Chatham Railway, shared under CC BY-SA 4.0.3