IN 1930, a new crossing over the River Forth was proposed.

Councillors from Clackmannanshire, Stirlingshire and Fife consulted on a bridge to be located either at Alloa or Kincardine.

In the end, monetary factors prevailed with projected costs for a bridge at Kincardine being £30,000 less than the Alloa option of £418,000.

The Cleveland Bridge and Engineering Company won the contact and the first sod was ceremoniously lifted on December 20, 1933 by Lord Bruce, the eldest son of the Earl of Elgin and Kincardine.

Local labour was employed and, at peak, 210 people were working on the bridge project and associated access roads.

Piled timbers and working platforms were placed at either side of the structure so materials could be easily transported to the site.

The concrete pier foundations were built within steel cylinders measuring 14 feet 6 inches (4.5m) in diameter which were sunk into the river bed with the top protruding above the high tide mark.

Excavation within these cylinders was limited to low tide and continued until rock was reached and the permanent concrete piers built inside.

The completed swing section, weighed in at 1600 tons, 364 feet (111m) long and around 80 feet (24m) high, all supported on concrete cylinders.

Rotation was by means of two vertical pinions operating on a rack fixed to a lower track and the two sets of turning machinery were housed between the track and the roadway, each operated by a 50 horse power motor.

There was also hydraulic equipment for operating the wedges and locking bolts.

In the event of a power cut, a 150 horse power diesel engine was available.

The whole system was remotely controlled from a cabin 30 feet (9m) above the road in the centre of the span, which also contained cooking facilities, heating and water for the operator and his assistant.

Three teams worked 8 hour shifts ensuring the bridge was manned 24 hours a day and when open, ships could pass around high tide causing just a few minutes disruption to traffic.

In terms of financial contributions, Fife Council paid approximately 50 per cent of the cost, with Stirling paying 25 per cent and Clackmannanshire 10 per cent.

Dunfermline and Falkirk contributed the rest.

The bridge was officially opened by Lord Bruce on October 29, 1936.

The swing mechanism last operated on November 6, 1987 and in 2005, the bridge was given Category A Listed status by Historic Scotland.