A teenage boy has died while riding a quad-bike in a field in Oxfordshire.
Tim Hobill, 16, was found seriously injured when police arrived in the grounds of Ditchley Park, Enstone, near Chipping Norton, just before 1800 BST on Tuesday.
Attempts were made to resuscitate him but he was pronounced dead shortly after.
The teenager, who had just finished his GCSEs, worked weekends at Ditchley Park - once a weekend retreat of Sir Winston Churchill's.
His father Robert Hobill runs a farm on part of the estate and his sheep and cattle are allowed to graze in the grounds.
Christopher Galloway, bursar of Ditchley Park, said:
"It was a very, very tragic accident.
"Tim was rounding up the sheep on the quad bike when somehow it turned over on top of him.
"The ground is a bit rough there and there are some logs around but we don't know exactly how it happened.
"Tim was a very, very nice young man. He had just finished his GCSEs and was moving on to the sixth form."
Thames Valley Police are carrying out an investigation into the accident.