Stansted branch gradients are shown as percentages. Looks like there are 800m+ of 1.5%, or 1:66.
Thanks for this.
It is quite complicated with different sources using imperial and metric measurements. I have tried to convert everything to metres to match the Ordnance Survey.
The Sectional Appendix shows 61 chains between the tunnel portal and the platform 1 buffer stops. That's about 1220 metres.
However, platform 1 is 359 metres long so it is only 862 metres between the tunnel portal and the end of the platform.
Furthermore, there are also the crossovers at the platform ends, these are unlikely to be on a steep gradient. The distance between the tunnel portal and the crossovers is 34 chains or about 680 metres.
At 1 in 66 the line can climb about 10 metres in that distance. The graph in the link suggests only about 8 metres.
The graph also implies that inside the tunnel is not level track, but the increase in height from the west end to the east end is only 2-3 metres. Without knowing how that graph is compiled it isn't possible to be sure whether this actually reflects what's on, or under, the ground.
At the other end of the tunnel the Ordnance Survey suggests that the line is about 90 metres above sea level. The 90 metre contour is near the tunnel portal, where the line is in a cutting, and there are two spot heights nearby at 93 metres and 94 metres.
I am now convinced that Stansted Airport is the highest point of Greater Anglia, higher than Elsenham or Ingrave, but I'm still not convinced that the buffer stops are 107 metres above sea level and at roughly the same level as the runway.