UKIP's millionaire donor told us that he will keep giving money to the party
Banks, who donated £1 million ($1.3 million) to the anti-EU party and co-founded the Leave.EU pro-Brexit group, told Business Insider that James would "professionalise" the party and lead it to a bright future.
"I was delighted and Nigel was as well," he told BI at the UKIP conference in Bournemouth.
James was elected after receiving nearly 50% of the membership's vote. The result comes after weeks of in-fighting over the NEC's decision to block Steven Woolfe to stand in the contest after failing to submit his application on time.
Banks played down the row and told BI that James' leadership will mark a fresh start in the party.
"We were relieved but I don't know why people were upset - it was only four or five people in the party who were causing problems. But these problems have been firmly put to bed. The line has been drawn underneath it."
He added: "By the way, I think she'll deal with some of the people who are causing problems in a way that Nigel didn't."
Farage will continue to serve as an MEP but is standing down as leader after first being elected in 2006. He said he intended to go abroad and help anti-EU parties across the continent, at an event BI attended on Thursday evening.
Banks believes the party should do something similar. "We've talked about going continental and visiting other European countries and help them with some of the things they've got planned."
The businessman became a big name in right-wing politics when he donated £1 million to UKIP in 2014, having formerly supported the Conservative Party. He told us that he fully intends to keep giving the party financial backing.
"Yeah, I mean absolutely. It's been a great result and I think the future for UKIP is fantastic," he said.
"Diane [James] will be different. Nigel I think was great in the same way as a wartime leader. Diane has got a different tone but she's steely. She'll get to grips with stuff really quickly. She'll give everybody a chance. Her election thrills me because she will professionalise the party, which is what so many of us have been asking for. She'll get us organised and make things happen."
One of the key talking points at the conference, which was attended by hundreds of party activists and members, was Brexit and the prospect of Theresa May delivering a deal which won't satisfy the demands of UKIP voters - referred to by James as a "Brexit-light" deal. Banks said he shares these concerns.
"I'm very worried. I don't think they [the government] actually understand the single market. It's not really a single market - it's a protected customs union for the European Union. We need to get out of it as soon as possible, trade with our neighbours, and reach our own trade deals."