The Icknield Way is the oldest road in Buckinghamshire and in its earliest form was in use from around 3000BC.
The apparition here is said to be none other than Queen Boadicea, riding her chariot towards the site of her last battle. It is believed that this took place somewhere near the junction of the Icknield Way and Watling Street.
For further information, please read Haunted Places of Bedfordshire and Buckinghamshire by Rupert Matthews.