Duncan (pictured) was based in Eastbourne and a partner at The Personal Mortgage Service, having spent more than 20 years advising clients on mortgages.
He was one of four partners at the firm, along with Greg Abbot, Malcolm Davies and Gary Price.
Both Davies and Abbot had worked with Duncan for more than 20 years and said he would be very much missed.
“I miss him terribly and can’t believe he’s gone, you couldn’t wish to know a nicer person,” said Davies.
“He was very knowledgeable and very good with clients – they can’t speak highly enough of him.
“And he always had a glass half full attitude to life, so I’ve got tremendous admiration for how he handled his illness.”
Abbott echoed these views about Duncan’s passion for helping his clients, noting: “He was very customer-orientated and went the extra mile by taking on a lot of difficult cases
“And he got involved in the industry and sat on forums which was a credit to his approach.”
Fellow partner Garry Price said: “Stuart was a loveable character.
“His knowledge of the industry was second to none, especially with quirky criteria and he would leave no stone unturned to find a way forward and to get a solution.
“He would always challenge the establishment at conferences – asking the important and awkward questions and he was always first in the queue to offer someone help if they needed it,” he added.
Anyone wishing to attend Duncan’s funeral is welcome and should contact The Personal Mortgage Service for details.
Tributes also poured in for him on the Cherry forum where Duncan was a frequent commentator and regular source of support and assistance.
Cherry director Donna Hopton agreed that Duncan’s ethos was always to put his clients first and it was clear that their best interests were paramount.
“Sometimes this led him to conflict as he wanted to get what his clients wanted and needed as quickly as possible and box ticking was very much secondary,” she said.
“Stuart was immensely knowledgeable and was always happy to share his wisdom, always generous and helpful on Cherry, and keen to assist his colleagues thereon.
“Stuart had strong views and was not a yes man – his judgements were always considered and balanced and his views well respected. He never, ever, just accepted things he felt were wrong.”
Hopton added that reaction on the forum showed how admired Duncan was and what everyone thought of him personally.
He was 61 years old and leaves a wife, brother and sister.