Esteemed lawyer Sir Peter Williams QC has died.

Widow Heeni Phillips-Williams said he died at his Ponsonby, Auckland home at 6.30pm on Tuesday, after a long battle with cancer.

She was being supported at home by family.

Williams, 80, was one of the country's best known defence lawyers and was knighted in December.

ALSO READ: Ailing Sir Peter Williams receives knighthood early

Phillips-Williams believed he knew he was going to die on Tuesday as he had called everybody he knew into his room, she said.

"I believe he knew he was going to go tonight because he called everyone around, including our two dogs, into the bed," she said.

Over the past few days community carers had been helping nurse Williams and the hospice had offered him a bed, but Phillips-Williams declined because she wanted him to be at home, surrounded by his loved ones.

He wasn't in any pain, she said.

Phillips-Williams said some of his last words were about his favourite pastime.

"He said to me, 'let's go off,' but he wanted to take his fishing rod with him," she said.

Williams was knighted in the New Year's Honours list in December. His investiture ceremony was to have been held in May but was brought forward a month due to his ailing health. It was held at his home.

President of the Criminal Bar Association Tony Bouchier paid tribute to Williams, a founding member of the association.

"It's really sad. It's a sad day for justice in a lot of ways, because he was the epitome of a lawyer whose full focus was on justice and making sure people had a fair hearing in court," he said.

"He was the most courageous lawyer the country's produced in my opinion. Nobody intimidated him. His clients, the police, the judges, nobody."

Bouchier recounted a case where he was giving evidence as a police officer, and Williams was acting as a lawyer for a defendant charged with a drug offence.

"I've got to say I was absolutely amazed at the quality of his advocacy in that case. His closing address, I was just mesmerised."

The defendant was found not guilty.

Williams' law career spanned 60 years and saw him represent some of New Zealand's more notorious criminals, including Mr Asia boss Terry Clark, and machine-gun murderer Ronald Jorgensen.

He was instrumental to the overturning of Arthur Allan Thomas' wrongful conviction for the killings of Harvey and Jeannette Crewe.

He was also an active member of the Howard League for Penal Reform and campaigned tirelessly for the rights of prisoners.

He detailed many of his cases in a recently published book,The Dwarf Who Moved, and was last seen in public at the Auckland Writers Festival held in May.

A LONG CAREER