Ambulancemen, who were summoned to Windsor Great Park shortly before 7am, discovered the injured woman lying naked at the foot of the huge oak tree.
First on the scene was Alastair Chamberlain, a Crown Estates park ranger, who hurriedly looked for a blanket to cover up the injured woman.
As she was taken to Wexham Park Hospital in Slough, Berkshire, she explained that she had fallen after an all-night sex session with her boyfriend, high up in the branches of the tree in the Cavalry exercise ground.
A spokesman for Windsor Great Park said yesterday: 'The young couple had apparently gone to the Great Park for a bit of nookie and had decided to climb the oak tree to add a bit of spice to the session.
'As they reached the height of their passion, the woman slipped from one of the branches at the top of the tree and plunged to the ground.
'It was a very clear case of coitus interruptus.
'Her boyfriend climbed down and found she had suffered a broken leg.
'Both of them had been completely naked in the tree and he hastily pulled on some clothes and ran to a phonebox to call for help.
'It was early in the morning and there were very few people about. The ambulance crew couldn't believe their eyes,' he added.
Park officials and the Royal Berkshire Ambulance Service have not released the couple's names to spare them embarrassment.Reuse content