It would have been funny if it had been a sketch from one of Rik Mayall's madcap comedies.
But while Rik thought he was being hilarious, his wife Barbara wasn't laughing.
Driving behind the ambulance tranferring him to a London hospital from one in Devon, she couldn't help but worry what the future held.
First Rik started pulling faces at her through the window, and then he pulled his trousers down and tried to moon at her.
"I thought I was being incredibly funny, acting like some drunken football supporter in a coach on the motorway," says Rik.
"In my mind there was nothing wrong with me. I couldn't understand why I was in the ambulance and not in Barbara's car going home. I thought everyone else was crazy, not me."
That Rik was capable of such antics just ten days after the quad bike accident which had almost killed him was remarkable.
His recovery had amazed doctors who'd told Barbara that many people had died from severe head injuries like Rik's.
But amazingly a brain scan had showed that one deep tissue haemorrhage had started to heal itself.
The second - a large resevoir of blood between the brain and his skull - was still there and if it didn't heal itself Rik would need to have surgery.
That prospect of a risky operation was almost as worrying as the bizarre behaviour Rik had displayed since he'd come round - four days after the accident.
With no recollection of what happened, and feeling physically well, he couldn't accept that there was anything wrong with him - despite all the evidence.
His short-term memory was temporarily affected and his attention span was limited. Nothing he was told sunk in. He started to think everyone was crazy - except himself.
Convinced he was as right as rain, he was determined to escape from his 'captors' and go home. Soon he was going to get the chance.
After a three-hour journey, Rik, 40, was checked into a private hospital because it was small, quiet and out of the way.
Barbara, 42, made sure he was settled then went back to their London home to be with their children Rosie, 11, Sid, nine, and Bonnie, two.
"Although Rik was making wonderful progress, he was still someone with a serious head injury and he needed to be in hospital," says Barbara.
"We moved him back to London because the kids were going back to school.
"We'd spent Easter in Devon, on our farm where the accident happened, but now it was time to go back and we wanted Rik near us.
"But the private hospital was a mistake. It was too much like a hotel and it just re-enforced Rik's belief that there was nothing wrong with him. It was too easy for him to escape from."
Rik continues: "I didn't know where I was. I felt I was in a very strange place, it was like a surreal dream.
"There were these long corridors and I remember walking around wondering where everyone was. I felt like a prisoner.
"It was a very eerie feeling and for some reason I thought: 'I shouldn't be here, I should be somewhere else.'
"I decided to go for a drive around London, and I escaped, I finally escaped. I couldn't tell what was real and what wasn't.
"I had a jacket on and some training pants and I just went downstairs, got in a taxi and said: 'Take me home.' In my 'mad' head I just had to get away."
The phone rang at the Mayall's London home and Barbara picked it up. It was the private hospital. "They said to me: 'He's gone,' and I said: "What do you mean, he's gone?' and they went: "He got into a taxi and we don't know where he is," says Barbara.
"I was beside myself with worry. He could have gone anywhere. It was only ten days after the accident and six since he'd woken up. He was still very much off balance, anything could have happened."
But within an hour of Barbara putting down the phone, as she was still frantic with anxiety, Rik turned up on the doorstep.
"I was just so completely relieved when I saw him standing at the door. I was terrified, but so relieved.
"I'd been so frightened for him, and furious that he'd been able to just walk out and get in a taxi," she says. "He just went: 'Hi darling, where are the children?' and I just pretended everything was completely normal.
"He had no money, so I went out and paid the taxi. He went into the sitting room and sat down with Sidney who was watching television.
"Rik went: 'Hi Sid,' and Sid said: "Oh hi, Dad,' and they had a cuddle.
Rik wasn't really with it and he got very concerned that the kids were hungry and ordered a pizza for them. He couldn't have been happier.
"Then I gave Rik a kiss and said: 'Come on darling, it's time for bed,' and took him upstairs."
At 12pm, while Rik was sleeping, Barbara phoned her GP, Christine Elliot, who, despite being eight and a half months pregnant, immediately came round.
"Christine was absolutely brilliant. She gave him a strong sedative and then - heavily pregnant - had to almost wrestle him down four flights of stairs to an ambulance.
"They took Rik to the Charing Cross Hospital where he was placed under the care of consultant neurosurgeon Mr David Peterson," says Barbara.
The following week scans showed that one of the haematomas had almost completely gone.
Rik started to calm down and his behaviour normalised.
"My mood started to change from elation, that feeling of being happy to be alive and wanting to escape," says Rik. "I was starting to get bored with being injured and not being the me I used to be.
"I was much saner by now and I realised that if I was going to effect a permanent escape, it would have to be more profound than just running away."
The comic adds: "I said to Mr Peterson: 'Look I can recuperate just as well at home as I can here,' and after they'd kept me under observation for a week he said to me: 'Well yes, you may as well be at home'."
Rik still had a reservoir of blood under his skull which might need surgery, and the threat of that hung heavy on his mind.
And as the reality of what had happened to him - and what could still happen - started to sink in, his manic elation disappeared. "My emotions were changing. I wasn't brain-damaged but my brain had been affected in some way," he says.
"I was walking and talking - still sometimes saying the wrong words - but I was really quietening down.
"I was very thoughtful, I won't say depressed, but a couple of times I felt really down."
Because he was unable to drive, Barbara picked Rik up from the hospital in his Mercedes and took him home.
After a couple of days in London, Rik and Barbara decided to go back to Pasture Farm in Devon for the first time since the accident happened.
It was their dream home, the one they'd fallen in love with and bought only nine months earlier. They had no intention of selling it because of one freak accident.
The quad bike which had nearly killed Rik was still in the garage and he went to confront it.
"At first I wanted to throw it off a cliff, it was just sitting there like an ememy of the family," says Rik.
"But I realised it was only a machine and I was a little insulted at how small it seemed.
"I was overcome with this terrible feeling of sadness. That I had altered my life and that of my whole family because I was stupid enough to fall off a bike."
For Rik, the physical recovery from the accident was well under way. But at this moment his emotional recovery was only just beginning.