A woman's body has been found in a lay-by just outside the M25 in Buckinghamshire.
Thames Valley Police has launched an investigation into the unidentified woman's death, which they are calling "suspicious".
A spokesman said detectives do not yet know what killed her, with a post mortem due to take place tomorrow.
A passing motorist raised the alarm just after 8.30am and police descended on the Amersham Road, Gerrards Cross, shortly afterwards.
Supt Yvette Hitch said: "Officers are at the scene working to establish the circumstances surrounding the woman's death.
"We are in the very early stages of our investigation. I would like to speak to anyone who has any information about this incident or who may have seen anything out of the ordinary in the area.
“We are working with the Highways Agency to minimise disruption in the area. A scene watch remains in place."
Anyone with information is asked to call police on 101, or to phone Crimestoppers anonymously on 0800 555 111.
