It was unbearably hot and steamy in the green, canvas tent where more than 200 people were crammed; every inch of sitting, standing or squatting room was taken up, with all eyes trained on a small wooden stage.
And yet still more tried to wiggle in, faces peered around flaps, contorting for a glimpse of the funny woman who was about to go straight, the High Priestess of Hysteria who was going to teach us all to stay calm.
You could feel the adrenalin rush in the audience when, at last, our speaker appeared, seating herself casually on a large black speaker case, resting her small feet on the basket weave chair in front, next to bright lights spelling out "NOW" - the name of a new arts and wellbeing event taking place alongside the Wilderness Festival in Oxfordshire.
The crowd's level of enthusiasm was ironic given that we were there to learn how to temper our emotions at a workshop on mindfulness - the art of living in the present - but understandable. It was being led by Ruby Wax.
Yes, really. The comedienne, actress and writer is now a qualified expert in mindfulness, the psychological tool that uses the focusing of attention and awareness to overcome mental agitation, anxiety, stress and the sort of black depression that dogged her for years.
Wax, 62, put herself through five years of study on cognitive behavioural therapies and psychology, and now holds an MA from Oxford in the subject.
Leading her first-ever workshop, Wax was hilarious, authoritative, heartbreaking and generous in how much she shared with the audience.
Above all, she seemed composed and assured, in a way that fans who remember mad-cap Ruby - rifling through Imelda Marcos' shoe cupboard or Fergie's colour-coded knicker drawers for her eponymous TV shows - would find hard to recognise. Her early popularity was based around that urgency, mania even, in her humour and interviewing style, the brash, loud, American stereotype, apparently unabashed by convention.
But as Wax revealed to her audience, that was an illusion: most of the time and especially on stage, she was often in a state of mental disarray, her lines forgotten, caught up in the terror of not feeling liked, looking at all those expectant faces and thinking "you all hate me".
Her life was dominated by inner critical voices until she had a breakdown and was diagnosed as bipolar in the early 1990s. Years of therapists, counsellors and medication followed.
"Mindfulness keeps me on a plateau," she told me after the workshop, as we sat trying to ignore the endlessly distracting and competing sounds of the vibrant Wilderness Festival going on around us.
It is being aware of the moment, the now, and using that to calm our over-anxious amygdala - the area in the brain which hosts our emotions - which modern life otherwise keeps in a constant state of high alert, she explains. Wax, like many creative people, found that sense of adrenalin-overload exhilarating and addictive.
"But our brains have no braking system," she adds, and her aim now is "to keep off the tightrope between highs and lows".
"No one can keep that up - we are not born to be happy. Yes, we are born to have moments of bliss, but not to live in that state."
If Wax does feel depression creeping on, she knows now to find a peaceful spot in her home, turn off the lights, avoid sounds, smells, anything that stimulates the brain into further intense activity.
She believes that creating this calm physical environment at moments of internal agitation helps her avoid depressive episodes, too, and has kept her healthy for five years.
Learning mindfulness has had other unexpected benefits. "Ten years ago, I couldn't have done something like this," she confides. "I would go on stage in a state of fear, and start talking fast, and the audience smell fear and laugh at that."
The workshop was plotted minutely in advance, researched, edited, but not committed to memory like a script. "I just drew from my notes," she explains. There was no going blank or forgetting her lines. No "dying" on stage.
This aura of practised calm around Wax does not mask every emotion. She acknowledges lifelong feelings of intellectual inadequacy during the workshop - "I didn't even graduate from Busy Bees nursery," she quips.
Even the joy of achieving her MA, not to mention the knowledge base that allows her to banter about the intricacies of brain chemistry with the audience, doesn't negate her need for approbation afterwards.
"Did it work? What did the audience think?"
And at times her dark eyes fill with anxiety, memories of old fears perhaps returning to haunt her.
Mindfulness does indeed seem to be part of the zeitgeist. Among the distinctly middle-class crowd (Wilderness is also known as "Poshstock", because it attracts the likes of the Chipping Norton set) drawn to attend Wax's workshop, most were women in their thirties and forties who appeared to soak up Wax's explanation of how mindfulness works.
For much of the hour-long session Wax led the group through exercises, including focusing on one sound at a time, or urging us to feel our feet planted into the earth. It is important to focus on a single sense at a time, she explained, as that anchors the mind to the present. "You can't hear yesterday; you can't feel your feet in one hour's time," she told the audience. The tent was pin-drop quiet; I focused on what I imagined to be the sound of my own sweating.
"Our minds are only empty when we are dead," she warned. "Notice how your brain is trying to get your attention back. It will wander all over the place if you let it. So when we focus on a sound, the brain will start asking what is that sound, why is it like that, what else can I hear?
"Forty-seven per cent of our time, our mind is off wandering. And you know what is sad about that? Tests show we aren't having lovely daydreams. They show we're not enjoying that time. We are ruminating and worrying."
Wax proved herself a good teacher but the workshop is not about kick-starting a new career as a celebrity self-help guru; instead she intends to combine talking about mindfulness with her stand-up career (there will be a tour next year). She has written a book, Sane New World, as a guide to improving your own mental health. She seems genuinely evangelistic.
"We all need to learn how to cool down our own system," she said.
Her final instruction to me as we parted was to practise mindfulness a couple of times every day to get the benefit. "It's like your pelvic floor exercises," she confided, visibly pulling up her abdominal muscles northwards. "No one will know you are doing it. Take a moment to be in the now when you're waiting in the car, or in a queue. It takes practice but you don't get a six pack with one sit-up."
Wax may still be a joker but she's no fool.
• Years of therapy and counselling led Ruby Wax to a strategy to cope if she feels depression creeping on.
• She knows now to find a peaceful spot in her home, turn off the lights, avoid sounds, smells, anything that stimulates the brain into further intense activity.
• She believes that creating this calm physical environment at moments of internal agitation helps her avoid depressive episodes, too, and has kept her healthy for five years.