HELD as an “iconic” piece of Scotland’s industrial heritage, the Kincardine Bridge will turn 80 years old this weekend.

Spanning the River Forth between Airth and its namesake town, the bridge was the first road crossing downstream of Stirling, completed nearly 30 years before the Forth Road Bridge.

It was built with a swinging central section which allowed larger ships to sail upstream to the port at Alloa.

The crossing was a record-breaking engineering feat as it became not only the longest road bridge in Britain but had the largest swing span in Europe.

And in another first, photo electric cells were also used on the bridge to control the exact location of the swing span – it was so accurately set on its track that its 1,600 tons could be turned through 90 degrees by “three farthings’ worth of electricity”.

The 2,696ft crossing was formally opened on October 29, 1936, with hundreds of people, despite poor weather, going along for the spectacle.

The switches were operated by the Earl of Mar and Kellie, convener of Clackmannanshire; the Earl of Elgin, convener of “Fifeshire”; and Mr C E Horsburgh, convener of Stirlingshire.

And with a siren’s blast for fanfare, the huge span moved for the very first time at the stroke of noon.

In his address 80 years ago, Lord Elgin said the project was spearheaded by the Fife, Stirling and Clackmannan counties – with “special credit” due to Clackmannan for abandoning its plans to build a crossing at Alloa and committing to Kincardine.

It was last opened 29 years ago, and shortly after that was fixed shut in 1989.

And despite the construction of its sister crossing slightly upstream in 2008, the Kincardine Bridge remains a vital part of the area’s infrastructure and of Scotland’s industrial heritage.

Miles Oglethorpe, head of industrial heritage at Historic Environment Scotland, said: “Although it opened as a swing bridge for the last time on November 6, 1987, the Kincardine Bridge remains a very important and iconic piece of central Scotland’s transport infrastructure, despite the opening of Clackmannanshire Bridge in 2008.

“Completed by the Cleveland Bridge & Engineering Co to the art deco designs of Sir Alexander Gibb & Partners in 1936, it was the first road bridge to be built over the River Forth downstream of Stirling and was therefore a hugely significant transport link for many decades.”

In 2005 it was listed as Category A by Historic Scotland.