"I didn't have a goal, I just wanted to talk to people about what I was doing here," he says. "I wanted to establish something that would help me connect more because I realised I was becoming increasingly out of touch with what was going on back home."
Having lived in England for more than a decade, working on the festival has helped Slack rediscover his Kiwi roots. "Since the whole thing got under way, I've been sharing information with my dad and I've been learning more about what he knows, such as his Maori connections. I didn't know that he can speak Maori really well because he grew up with Maori people. This is all really surprising stuff.
"One of the sessions we're doing is with Peter Alsop, who helped put together Selling the Dream, a beautifully illustrated book of posters that Tourism New Zealand used to sell New Zealand to the world over the past 40 years. It puts the relationship between New Zealand and Britain into a fascinating social context. I sent some of those images to my dad and he was like, 'I grew up with that poster!"'
Other New Zealanders attending the festival include Fay Weldon (who has long been based in Britain), Stephanie Johnson, Fleur Adcock, Paula Morris, Ian Wedde, Witi Ihimaera and C.K. Stead, who will appear on stage alongside his daughters Charlotte Grimshaw and Margaret Stead. Graphic novelist Sarah Laing will hold a workshop and will talk about biographical comics alongside Australian Evie Wyld.
"Someone was asking me for a list of the New Zealand-only events that we're doing but I was only able to find about three," says Slack. "The vast majority of the programme is really about joining all that together and where possible we've tried to bring in non-New Zealand and Australian voices as well."
Along with Australians such as Clive James, John Pilger, Tim Winton and Kathy Lette, the festival will also feature contributions from British talents like Nicholas Shakespeare, Val McDermid and Skyfall actor Ben Whishaw, who will take part in the closing night performance of the biblical poem, Song of Solomon, which will be set to music composed by his Australian partner, Mark Bradshaw.
"Anyone who is in this festival has a connection, whether it's that they've visited either country, like Margaret Drabble, who was in Adelaide and Wellington earlier this year," says Slack. "She is actually a huge fan of Janet Frame, so that's why she is in that event. We're trying to explore what Australia and New Zealand mean to British people so it's really important we don't just pop famous people in there for the sake of it."
Festival
What: The inaugural Australia & New Zealand Festival of Literature & Arts
Where and when: Kings College, The Strand, London, May 29-June 1; Going Bush Festival of Short Plays, Bush Theatre, Shepherd's Bush, May 23-24
Web: http://ausnzfestival.com/