A lorry driver is in a serious condition after being stabbed in a lay-by.
The 45-year-old was attacked from behind as he got out of a lorry in Sutton Road, Haddenham, at 07:20 BST.
The attacker is described as a white man, who was about 6ft and of medium build. Police said he may have fled the scene in a vehicle.
The lorry driver was taken to Addenbrooke's Hospital with injuries described as "not life-threatening".
Nothing is believed to have been stolen from the lorry, which was carrying bread.
Det Sgt Phil Richardson said: "The lorry is very distinctive with the word 'savage' on the side.
"I would like to hear from anyone who may have seen someone hanging round this vehicle or fleeing from it."