Lisa Driver, a mother of two in her 40s, suffered a skull fracture which left her with epilepsy after landing at the bottom of the moat at the Roman Painted House in Dover, Kent, in the early hours of July 15 2007.
Dover Roman Painted House Trust and Dover District Council denied liability for Mrs Driver's injuries, claiming that she was a trespasser and the author of her own misfortune.
Today, Judge John Leighton Williams, at the High Court in London, said Mrs Driver was a trespasser in law and rejected her claim that the site was dangerous.
He added that, even if he had decided in her favour on liability, he would have found a higher than 50% degree of contributory negligence on her part.
Mrs Driver has no memory of the accident but her friend, Elaine Bristow, said that they were not drunk although Mrs Driver had consumed five vodka and Cokes - two at home and the rest in three different pubs.
She told the court that they went into the private car park at the closed site, while they waited for their taxi, as Mrs Driver wanted a "wee" and had been told she could not use the taxi office's facilities.
"When she went around the corner, I knew what she was going to do and I said 'you can't wee here' and we walked to the wall."
Mrs Bristow said she stopped Mrs Driver because she would get a fine if a police car came along and saw her urinating.
The Trust's counsel, Philip Williams, suggested that they had been "on the pop" that evening for six and a half hours, but Mrs Bristow said they only had single measures as doubles were too expensive.
The judge heard there had been no other accidents since the 3ft wall was built almost 40 years ago although an estimated 650,000 visitors had passed through the site during that time. The wall was in good condition, painted white and readily visible.
The judge said that, as a witness, Mrs Bristow "was a little protective of the claimant with a tendency to argue".
"I am not satisfied she has an accurate memory of the detail of what happened that night.
"Maybe because she wasn't asked until two years after the event, but I suspect that drink too played a part."
He was not satisfied he had heard a true account of how much each woman had drunk
"I find it surprising they limited themselves to only three or four drinks in the four and a half hours they spent in Dover before the accident."
Mrs Driver's agitated search for somewhere to "wee" in the car park told him that her judgment was impaired and she probably attempted to climb over the wall to relieve herself on the other side.
He said: "Where urgency exists it rarely vanishes into thin air."
While there was obvious sympathy for Mrs Driver, whose injuries had blighted her life and prevented her return to work as a teaching assistant, that was not enough for her case to succeed.
At the completion of the hearing the judge addressed Mrs Driver and wished her "good luck for the future".
Asked for her reaction after the ruling, she commented outside court: "To be honest with you it was the outcome that I was expecting.
"It was what I was expecting so, you know, life goes on for me. Nothing is going to change."
Smiling, Mrs Driver, 47, from south-east Kent, added: "I am still here, and I am not dead - that is a positive!"
It is understood that she was on a no-win, no-fee costs arrangement.
She left the Royal Courts of Justice in a wheelchair.