Stumbled across this bridge today during a visit to Wycoller and recognised it from this website.
It is easy to find if you were looking for it and it is just a bridge across a small ford. It was repaired in around 1989 after it collapsed and it is now held in with an iron bar which is visible.
There is not much water in the stream so the bridge hardly seems necessary but it may have had another purpose or the stream may have had more water many years back therefore justifying the bridge's existence.
I have added a pic of me on the bridge (blue fleece) so you can see the size of the bridge compared to a 5 foot 9 man.
I stumbled Across this site an Iron Age Bridge still in use today!
Unfortunately I didnt have my camera this time. It's basically a cut stone slab lying across a Beck near Wycoller Hall.
There's some ambiguity over the age of Clam Bridge. Some sources identify it as Iron Age, while others go for a much later date. Here's a description of the bridge from the Lancashire Council web site:
The Clam bridge is a single gritstone slab laid across the beck with small holes on one side showing the former position of handrail supports. The bridge is believed to be more than 1000 years old and is a scheduled Ancient Monument. On may 19th 1989 there was a cloud burst on Haworth Moor and Boulsworth Hill above Wycoller and in the resulting flash flood the stone slab was swept from its foundations and cracked in two. The bridge was repaired and put back into position, only to be swept away and broken again in a further flood in August 1990. It was restored and replaced in June 1991.