The North Kent Railway, was built in 1849. This was originally planned as an extension of the L&G, but this would have meant tunnelling under the Royal Greenwich Observatory, and worries about vibrations from passing trains affecting observations led to it being diverted in a generous curve via Lewisham and Blackheath, to rejoin the intended route from Charlton and Woolwich onwards (although the original route via Maze Hill was subsequently built). To complement it, the Mid Kent Railway was conceived, branching off at Lewisham by a sharp curve and initially heading southwards, intended then to curve gradually east to the middle of Kent.