There's a pedestrian gate into the depot visible on Mapillary at https://www.mapillary.com/app/?lat=52.398869493994&lng=0.27116718318318&z=17&pKey=1135823570263917&focus=photo&x=0.21764170274042788&y=0.5353231648573348&zoom=0 so I assume the path exists (albeit restricted to employees/customers).