On the Mat.

Robert Bruce's bad guy wrestling antics were so convincing a spectator once attacked him with a knife during the halcyon days of On the Mat.

He also had bottles thrown at him and others tried stubbing cigarettes out on him.

But away from the biff and bash of pro wrestling, Mr Bruce led a life of loyalty, tenderness and compassion.

He passed away suddenly yesterday morning after a short illness.

He was understood to be in his mid-sixties.

His close friend, actor Temuera Morrison, said he had known Mr Bruce, who became his agent more than 20 years ago, "like a brother".

He said he was a pillar in the film and television industry.

"He wasn't just our agent, he was our brother and everybody who knew him knew he had a strong sense of loyalty, it was probably because of his Scottish roots.

"He really cared for all of us, this was the man who went to China and brought Kevin (Smith) back," he said.

SPCA chief executive Bob Kerridge said Mr Bruce was "a gentle giant", who was actively involved in promoting the welfare of animals and later became vice-patron of the Auckland SPCA.

He said the Scot would mentor young children at school assemblies around Auckland and would often visit the elderly on behalf as part of the organisation's outreach programme.

"He was such a compassionate person," said Mr Kerridge.

"He could have quite easily crushed your skull in one hand and held a kitten in the other."

Born and raised in Musselburgh, near Edinburgh, Mr Bruce started wrestling in London in 1967. He later toured the world on various wrestling circuits before he ended up in New Zealand in the early 1970s.

"He was a very technical wrestler who learned in some of the best schools," said New Zealand wrestling legend, John Da Silva, who first met Mr Bruce in the late 1960s in England.

"He was very, very tough ... he always conditioned himself well and rarely got out of shape."

Wrestling historian Dave Cameron said Mr Bruce was an old-school technical wrestler who "knew every move in the book".

He often played the bad guy - and played his part well.

"He was so bad and convincing that I think someone attacked him with a bottle as he was getting out of the ring ... on another occasion there were people who tried to stub cigarettes out on him."

His wrestling career was curtailed by elbow and back injuries but Mr Bruce, who had a bit-part in the 1970s movie A Clockwork Orange, continued his work in the acting industry and established the Robert Bruce Agency in 1978, nicknamed the Ugly Bruce agency.

Morrison said at that time his clients were his wrestling friends who later became pioneers in the local stunt industry.

"Whenever anyone needed some ugly people or some stunt work or fight sequences they called the ugly agency."

"Of course later on he got people like Kevin Smith and Cliff Curtis and the image improved," he said.

Mr Bruce is survived by his long-term partner, Gabriella. His funeral arrangements are still being decided.