Welsh said he had a “big connection” with Brighton, where he had lived briefly.
He said: “I thought it would be a great place for Lennox to move to once he had left the police force in Edinburgh, that it would be a clean break for him.”
The novel looks at the “post-truth society” and is full of the “dramatic language” he likes, Walsh said.
At the event he said he would be “chatting away” about the book, the characters and his writing in general.
He said he liked the events to be “quite interactive” and “for people to ask questions about anything they want to”.
“I think people think I would be bored by questions about Trainspotting but Iām not – people can ask anything they want to basically,” he said.
