When the Art Gallery of NSW launched its late-night program Art After Hours in 2003, it was an outlier. Not that Ashlie Hunter, who has been producer of the event for 13 years, knew until recently. “I found that shocking, to be honest,” she says.

Last year she was invited to contribute to a report by Culture 24, a UK organisation looking at late-night programing in museums to get a picture of how it’s done around the world. “I was interviewed and presented a paper, and what became clear is we were one of the first to offer it,” she says. “It’s funny, when you’re beavering away in your own world and then you look up and find out wow, we’re global leaders.”

Hunter says London’s V&A launched its program first, in 2001, but it was monthly. The Sydney version – which is weekly, free and first trialled in 2001 – came not too long after. “Not many [institutions] are doing such a content-hungry program as we are,” she adds. “We have new speakers, new music and new events every week.”

Each Wednesday night, the Domain gallery keeps its doors open until 10pm and, along with giving punters access to its exhibitions, library, cafe, restaurant and shop, it hosts talks, workshops, comedy, films, tours and live music.

“Art After Hours might be unashamedly populist, loud, fun and adventurous, but it’s also thoughtful and smart, and above all, inclusive,” she says.

The idea came about because the gallery was looking for a more accessible way for people to learn about art. It decided to create a more social and entertainment-driven program that would turn the gallery into a fun civic space and provide a new platform for people to look at the gallery’s work.

In its 15 years it’s invited guests including Tracey Emin, Benjamin Law, Christos Tsiolkas, Jane Caro, Jack Thompson, Annabel Crabb, Adam Goodes and Sarah Blasko.

To mark the decade-and-a-half, this Wednesday the gallery is throwing a party and has recruited two heavy-hitting Aussies to have a chat about creativity, art and why it matters. Musician, comedian, actor, writer and director Tim Minchin will lead a conversation with Ben Quilty. They will also chat about their respective experiences of the Archibald Prize, which is currently on show. Quilty took out the prize in 2011 with his portrait of one of Australia’s most celebrated artists, Margaret Olley, while Minchin was the subject of Sam Leach’s award-winning entry in 2010.

After they chat – and perhaps Minchin may play something on the piano – there will be cake and live music by the Speakers.

In the past two years, Art After Hours has collaborated with a number of other Sydney institutions such as Mardi Gras and Vivid – which Hunter says has allowed both parties to achieve something they wouldn’t otherwise be able to do. It’s also been a mainstay for Sydney’s alternate night-time economy beyond eating and drinking. “The program is very inclusive; it’s for everyone. We’re in a dark park and we still manage to attract between 1000 and 5000 people. It’s really great,” she says.

Art After Hours celebrates 15 years on Wednesday August 15 at 6.30pm, with Tim Minchin in Conversation with Ben Quilty. It’s free.