As any rehab graduate will tell you, there's no such thing as a quick fix, and in order to receive the full benefit of therapy it's advisable to take life one step at a time upon completion of treatment. Which is why it's heartbreaking to witness Robin Williams - having recently spent two months dealing with his alcoholism at a treatment centre in Oregon - contort himself today into a dizzying display of theatrics.
One moment he's channelling Al Pacino; next he's Barry White; now Marlon Brando, Method-acting into the inner psyche of a loner penguin. And he's only just warming up. Next he's singing opera in a Mexican accent before interrupting with the taunts of a gang of macho Latino penguins. Now, he's doing Arnold Schwarzenegger in a phone conversation with Henry Kissinger, discussing the merits of the Great Wall of China. You get the picture.
Williams has doubtless earned the film industry's full respect for soldiering on through his promotional duties in the face of personal adversity. But there's also a sense of watching a train wreck in progress.
In the past few weeks I've observed him tap-dance his way through press days for three very different films: the animated musical Happy Feet; political comedy Man of the Year and family adventure Night at the Museum. Today he's performing cartwheels on behalf of Happy Feet - the dancing penguin extravaganza that last month trounced Casino Royale at the US box office.
Directed by George Miller of Mad Max and Babe fame, Happy Feet tackles the disparate themes of environmental pollution and alienation; both subjects momentarily pausing Williams's high-speed repartee. "The world can't dump its garbage in the ocean because it simply can't absorb it all. It's a mess out there. We're poisoning the food chain, and that's a big deal." He seems to make a conscious decision to go with the gravitas of the moment: "Being an only child meant I was forced to be more of an adult than a child growing up, then it reversed in college where all of a sudden there was this sort of a freedom. I discovered an interesting thing called improvisation. And from that moment I went, 'Mmm, this is a lot more fun than economics...' and then 'there's women'. And so I found that thing which, for me, worked."
Sixty films later, Williams has proven himself not only as a comic, but as a versatile performer, earning a best supporting Oscar for Good Will Hunting as well as Oscar nods for The Fisher King, Dead Poets Society and Good Morning, Vietnam. Williams believes that this unrelenting drive left him prey to addictions: quietening the voices in his head with cocaine and booze during the Eighties. Williams clung to sobriety for almost 20 years, although found himself slipping back into the bottle over the past three years, finally seeking help in July.
"Most addictions and alcoholism are diseases of more, of wanting more. Rather than being 'Enough. This is good'," he reflects. "[Rehab] allowed me to spend some time contemplating. I was a spiritual person before and I'm more so now. In the way that the only thing that helps me at this point is God on that level - that's the way to get through it. When you have these problems it's usually a low brain thing and it re-wires that one immediately, and changes the method of your thinking quite quickly, and the only way to beat that is something that combines mind and soul which is spirituality, and basically prayer and meditation, and all these things that allow you to go 'I'm back'. And the great thing that you learn is that you're not alone.
"You come back from that and you go, 'Life is wonderful' And every day you're thankful and grateful, literally for what you get and who you are and all those simple things. And on that level, 'Yay! It's a great thing'."
When I compliment him on his obvious good-health, he can't resist a joke: "That's what rehab does - make you feel better. It's very quiet in rehab. They tend not to be loud places because there's people in recovery. I was in rehab with a lot of doctors which is always kind of disconcerting. It's like being in a fat farm with nutritionists where you wonder, 'if it didn't work for you...?' And if you knew how many doctors had addiction problems you'd be a little wary about going to the hospital."
The connection between comic genius and addiction is not lost on Williams. "I believe it's those darker aspects that enables some of us to look into the void - and to see the funny side. One of the greatest comedy performances of all time was Richard Pryor talking about burning himself alive, and then the guy going, 'Hey Richard, how about that last autograph?' That's pretty dark."
"Ultimately comedy is about being dark, about looking at the nastier aspects and laughing in the face of it. That's part of it. Many comics have been hardcore unrepentant alcoholics and addicts and some make it, some don't."
Having long since stopped basing his career choices on money, Williams worked for union scale on The Night Listener, later taking home just $1m (£513,000) for Man of The Year compared to $20m for 1999's Bicentennial Man. While many actors reach a salary peak and cling onto it as a token of self-worth, Williams generally follows his heart, although he'll likely return to the $20m mark for next year's long-awaited Mrs Doubtfire 2.
Man of the Year casts him as a popular TV host who skewers politicians on his nightly show - only to find himself elected as the next US president. "The fact that I briefly read political science doesn't qualify me in any way to be a politician. Because to be a politician you have to be politic. You have to be able to modify yourself and be appealing to many people on many levels but as a comic you don't have to worry about that much. I have that licence. I have kind of open season on everybody."
If Williams has never inspired the adoration of female fans then he understands that wit is often more powerful an aphrodisiac. Take his friend, Warren Beatty: "Warren is a handsome man and a brilliant man, but I remember when he was going to run once. I saw him speak, and he took 30 minutes to answer one question. It would be like Willie Nelson as secretary of agriculture. Pretty wild! Humour will always be an aphrodisiac because it implies a certain intelligence and a certain ease, and in relationships humour is as important as the other parts - the sensitivity, kindness, compassion and all the other things that build a relationship."
After a month of frenzied press duties, Williams looks forward to heading home to San Francisco to his wife of 17 years, Marsha Garces, and their two children. "I've got to take time off now," he concedes. "Part of the whole thing about going through rehab is that you realise that work is a compulsion, too. It's addictive, and for many men and women, it can be a behaviour that's rewarded but in the same way it's also unrewarding on a personal level. You can win all the awards in the world but do you have a life?"
One only hopes that he heeds his own advice. Ask whether he'd do things differently if he could go back in time and advise his younger self, he smiles: "I'd probably say, 'Don't do Popeye!' But then if I did that, I would have missed working with Robert Altman, which was a great experience. Seriously, what would I do? I'd go back and say, 'Don't drink!'"
'Happy Feet' opens on 8 DecemberReuse content