This southern section of the lengthy A34 links Winchester to Oxford and provides the first part of a vital freight route from the south coast to the north.
It was the UK's only single-carriageway motorway, and twenty years ago it ceased to exist. This is the story of the strange fascination it held, and of my place in history.
If you've ever been on the M62 across the Pennines, you'll know the one. It's the huge arched bridge 120ft above the road. And this is what it's like when you're standing on top of it!