A little summary of some of the history I’ve collated about the early years. it is hard to imagine a level crossing where the subway now is, but it was definitely there.
The station, then called Dartmouth Arms, opened with the line in 1839. There were two lines, one up and one down. They were along the lines nearest to present day Perry Vale. The new railway cut across the road joining London Road and Perry Vale(then known as the Bromley Road). This proved very inconvenient. Every time a train passed two gates were closed by a policeman to hold back traffic, in those days horse and carriage and I suppose horse drawn carts and trade vehicles
When years later the railway company eventually decided to put another two lines in, they built out to the west, towards London Road.
Only 4 years after opening, In 1843 the railway company decided they wanted to do away with the level crossing, which had been the subject of at least one accident. See the descriptions of the gates and the 1843 accident in newspaper articles below. They decided to tunnel under the railway to create a new route. They built a tunnel ( now the site of the Walrus mural) and road. The road was narrow, and much later they widened it added two new tracks and also raised the track bed substantially, I think in order to allow trams to use the route. we think of it as a bridge these days, not a tunnel. I’m not yet sure in what order or at what dates they did these things but I have a couple of rail magazines that explain much of it.
I suggest that on the Perry Vale side we can see the original station wall, with two brick pillars marking the original road across the railway. It seems likely that a gate was attached to one of these pillars. The railway was much lower then. Years later, when the track bed was raised, they would have built the wall upwards to match the new platform levels.
The first mention of the pedestrian subway I have found so far is in 1870. In a letter to the papers a local resident argues for a pedestrian bridge between Sydenham Park and Mayow Park, which would avoid the subway, described as ‘odious”. By 1879 a series of public meetings were held to complain about the state of the station, its carriage approaches, the subway which was muddy, unlit, and often a gathering point of local ‘bad characters’. The works would have to be negotiated between the railway company and the Board of Works for Lewisham. These two bodies did not seem to get along. It was in 1882 that the railway company eventually addressed the subway. But instead of just improving the footway which was step free, although with a gradient, they eventually installed steps which we have to this day. This was against significant public opinion, and the Board of Works insisted they had never agreed it, going so far as to seek an injunction to stop this.
I’ll be interested to know if anyone else has info about this period.