I don't know if people are aware that when the Highways Agency carry out major network upgrades, the land around the area changes ownership (some on a temporary basis, some permanently). This may, or may not, affect agreements people have in place with current landowners.
There is a page on the HA website highlighting the upcoming projects. These projects, whilst not changing the ownership of land, may also lead to temporary diversions of footpaths/bridleways etc.
http://www.highways.gov.uk/roads
Apologies if this is old news to people.