It is not the most obvious pairing.
"Sometimes you suddenly become aware that there is a naked person and you have got a pint in your hand," said Mavreen Arhun, 32, a frequent attendee. "Those two things aren't happening at the same time normally."
It can lead to some dicey situations.
Whiteson said he once had a model who downed three glasses of wine and three shots just prior to a class, leading to "the most terrifying and embarrassing two hours" of his life. The model kept arguing with Whiteson and refused to hold a given pose, frustrating the artists by staying in constant motion. Another time, a drunken interloper burst into the private area where they were having class and refused to leave for 20 minutes. Female models have had to fend off the occasional requests to do "erotic photo shoots."
But those situations are rare.The sessions are normally held in cloistered corners of the pubs so as not to scandalize passers-by or less artistic-minded patrons. (At one recent class held in the front of the bar with a window to the street, organisers had a model wear a bathing suit.)
"People are very civil and courteous," Crayford said.
On the surface, the appeal may seem to be its risque element. But Whiteson insisted that most people are there for artistic and therapeutic purposes.
"It's a nice way of being creative," said Amy Baker, 28, who studied art during college and values the opportunity to reengage with the skills she developed during her student years in a relaxed setting.
If the quality of the sketches is any indication, a number of the people who attend the drawing sessions have studied art at some point. But you don't need any skill to feel comfortable. The philosophy of the organizers is that life drawing is for everyone. Most of the pub classes are untutored. Of the three I attended, the majority of the students were female, and it appeared to be mostly an under-40 crowd.
"I definitely think people are rebeling against the digital age slightly," said Alessandra Ellis, 27, a graphic designer.
"People spend all day at work on their computers, and in the evening it's nice to sit down with a pencil and paper."
Ellis, who runs classes at the Old Dairy, a North London pub, calls the sessions "very relaxing."
That's because it's a whole-brain activity, enthusiasts say. The process of studying a subject and then drawing it forces the mind to toggle between instinctive and deliberate decision making. Ultimately that leads to "a moment where you forget about work and everyday life," Whiteson said.
Of course, the alcohol helps.
"It gets you more open," Baker said. Although if she has more than a few drinks, her attention begins to wander from her drawing, she concedes.
The pubs like it for financial reasons.
"It's been really good for business," said Jack Andrews, general manager of The Lion in Stoke Newington, the pub where Whiteson runs his classes.
"People that come to the life drawing come back on other nights."
After a smoking ban went into effect in London back in 2007, art became an attractive way to lure customers into the pub, said Tony Pianco, 50, founder of the Life Drawing Society. Pianco started hosting these classes more than a decade ago and has brought life drawing to more than a hundred different pubs, he estimates.
The bars make extra cash, and so do the models. The going rate is about $23 an hour, according to several models and organizers. However, the people posing get involved for more than just the money.
"It's a physical challenge to adopt interesting poses, and it's nice to be appreciated for them," said Hilary, a model who brought rope as a prop to help her create interesting stances. Another model said she does yoga and Pilates in order to have the core strength to keep still for the duration of a given sketch.
Hilary saw nothing exotic about the new setting for an old art form.
"Pubs have traditionally been a venue for all kinds of social events," Hilary said. "Lots of pubs have meeting rooms." Another attendee joked that adding drinking to every activity is the British way.
During my last class, Whiteson encouraged us to let the music guide our drawing styles - first, some sweet and melodic lo-fi tunes, followed by livelier jams and a heavy drum solo. I jibbed and jabbed my charcoal along to the rhythm. Suddenly, a burst of wild cheers from another corner of the pub - bar patrons watching soccer - snapped me back to reality. Then a waiter popped sheepishly into our room to deliver a plate of burger and fries to my friend. The whole class giggled. But then we turned our focus back to the music and drawing. That was what we were there for, after all.
"Instead of just getting drunk," Andrews said, "people are looking to do things with their time."