I grew up close to Shirtcliffe Woods. We had an Airedale Terrier, Madison (1995-2007), who we used to walk here. Unfortunately, she was scared of traffic, so if we wanted to walk her from one side of the stream to ther other, we would have put her back on the lead to walk right by the main road then back in the woods on the other side of the stream. We asked 'Friends of Shirtcliffe' if we could have a footbridge over the stream here for a safer and more enjoyable walk for all, which they granted! We therefore informally named it "Madison's Bridge".
The cache is a micro. You won't need to go under the bridge.
The Little Bridges series was started by Stanthews in 2009 to highlight small footbridges in remote parts of Wiltshire. Since then the series has been expanded by others all over the country and starting to spread fast. There is a stats listing run by Bloodsock, so you can see how many Little Bridges you have found, you can find it here:- https://littlebridgesseries.wordpress.com/ . If you would like to add to the series, please contact Stan on stanthews@aol.com and he will give you a number for your bridge, to qualify, the bridge must be a foot bridge too small for vehicles, please make sure your title exactly matches “Little Bridges # xxxx then the name” including spaces so it will get picked up and added to stats list.