The story of the B555 is somewhat confused. As far as I can tell, it started off as the road from Radlett to Hatfield. * The B556 went from Dunstable to Ampthill. * Then the B556 was renumbered as the A5120. * And then the B555 was renumbered as the B556. But why? UPDATE: This road is now part of the A1000. (any dates for the changes ?)