Is this the biggest bridge you've never heard of? As the A86 heads east through Glen Spean and on past the Laggan Dam and along the shores of Loch Laggan it is a road of many parts. Some sections seem little changed since Thomas Telford built the route 200 years ago, others display clear evidence of 1930s improvements, while other sections are much more recent in construction. The crossing of the Allt na h-Umaha above the western part of Loch Laggan clearly dates from the 1930s, the straightforward Concrete arch clad in local stone is characteristic of the structures that were erected across the Highlands in the 1930s.
The remarkable thing about this bridge, however, is its size. You are barely even aware of crossing a stream as you thunder along the A86, but if you have time, stop in the grassy pull-in and follow the anglers path south a little way to get a view of the bridge. The view from the road (left) does not do it justice, it is only when you look back from a distance that you see the sheer scale of the structure. It is not just a wide span, but crosses high above the stream which has cut a deep chasm into the rock far below. So next time you are on the A86 stop for a minute to marvel at this unknown bridge!
It is known that Telford built the Laggan Road as part of his Highland Roads and Bridges Commission. It is also clear, from maps and on the ground, that the A86 once passed ever so slightly to the south of its current route on the eastern bank of the river, and by following this alignment up to its end it is possible to identify where a previous bridge once stood. This was presumably the one constructed by Telford, although no record of it is currently known.
What does seem clear is that the old bridge must have survived into the 1930s, carrying traffic until the new structure was completed. Whether it was then demolished, or simply collapsed is not known, but either way there is no evidence of masonry in the stream below. The most plausible answer, therefore, is that due to the vast span and limited capabilities of Arch Bridges 200 years ago, the structure could have been a Timber Trestle bridge, perhaps similar to that surviving in Fort Augustus.