The Flying Scotsman crossing the Welland Viaduct

Let Alan Plumb be your host.

And let Wikipedia tell you about the Welland Viaduct:

Welland Viaduct lies on the Oakham to Kettering Line and carries the twin track non-electrified line between Corby and Manton Junction, where it joins the Leicester to Peterborough line. 

The route is generally used for the passage of freight trains and steam train outings. In early 2009, a single daily passenger service was introduced by East Midlands Trains between Melton Mowbray and St Pancras via Corby, the first regular daily passenger service to operate across the viaduct since the 1960s. 

The viaduct is also used as a diversionary route for East Midlands Trains mainline services using the Midland Main Line route. 

The line and structure, dominating this picturesque rural valley, are a favourite with steam train and heritage enthusiasts alike.

Oh, and:

Before the extensive privatisation of British Rail, repairs were regularly made to the structure by the Kettering and Leicester civil engineering staff. 

Many of the older bricklayers reported having seen the imprints of children's hands and feet in the bricks, from where they had walked on the clay-filled moulds before firing in the kiln.