The weather was just entering a long, fine, dry spell. As I worked away trying to do justice to the subject, a workman spoke to me.
"You should see what's like inside". Rhetorical obviously, since access to the site is exclusively for trained and cleared personnel, but it opened up an opportunity for a welcome conversation.
I gathered from this that the work involves re-placing some of the the 19th century metalwork in exactly the same style. Pieces are manufactured off site and installed. At the same time, shot blasting is carried out using grit under intense pressure to 'grind' away the dirt and old paintwork. Meanwhile the bridge, a vital transport link between London and Scotland, had to remain in use night and day.
The bridge is a Grade II listed structure of historic importance in the story of Britain's railways. The work reflects that significance in the great care taken. Environmental considerations also mean by-products produced by the work cannot be released into the surrounding land and air. (As I wandered under the bridge to photograph the scaffolding, a large bird of prey flopped out of a tree; flowers are punching through leaf litter to get to the sun; so something has been done right.)
Work was timetabled to last fourteen months, which means, if I have calculated correctly, sometime this summer the wrapping shroud will be removed and the bridge returned to view. Can't wait.