An elderly couple have celebrated their 40th wedding anniversary in hospital after an 81-year-old was knocked to the ground by a stranger.

Timothy Boydall was outside the St Heliers Library on June 30 when he was kneed in the back of the legs by an incoherent, muttering stranger.

His wife Josephine, better known as Marie, told the Herald he required surgery the day after the assault which broke a bone in his pelvis.

"It was not for money it was just a vicious, wicked attack," she said.

"We just feel people should know these things happen.

"You don't expect it to happen in St Heliers on a Sunday afternoon do you?"

Mrs Boydall said it would be a slow recovery for her husband who usually kept "very fit" and could be weeks before he returned home.

"His attitude is quite remarkable, a lot of people would be so bitter they would be groaning the whole time but all he wants to do is get up and go again."

Mrs Boydall was already in hospital herself at the time of the incident, meaning the two wound up spending their anniversary there together on July 2.

Due to the circumstances they were not able to properly celebrate but she was wheeled to her husband's bedside.

"It's all gone so quickly, I think we are still remembering July 2nd in 1979 [their wedding day]."

Josephine Boydall holding a picture of herself with her husband Timothy. Photo / Michael Craig

Mrs Boydall said she and her husband were grateful for all the support they received following the attack.

The bystanders who rushed to his aid were marvellous, she said.

Ambulance officers had even gone to the Boydall home to make sure the heater was switched off, she said.

One of those officers was St John Paramedic George Tyrell.

"The patient had expressed concern to us that the heater was left on at home while everyone was out," Tyrell said.

They wanted to give him some peace of mind and because time allowed they went to his house to switch off the heater and ensure the house was locked and secure, he said.

"It's not written in the handbook but we do this for patients out of goodwill and to reassure them however we can," he said.

"I'm glad that in this instance we were able to do a little extra to help the patient"

Tyrell has been a St John paramedic for 20 years and said helping people like Mr Boydall was why he did the job.

"I love meeting people and being able to help my community."

When police visited her husband they were lovely and even helped him top up his phone, she said.

"They were gorgeous weren't they?"

A police spokesman confirmed they received a report that an elderly man was struck in the knee by an unknown male on St Heliers Bay Rd on June 30.

"Police have made follow-up inquiries, including speaking with the victim as well as a witness to the incident," he said.

"Anyone with information about this incident is asked to contact Auckland City Police on 09 302 6400, or Crimestoppers anonymously on 0800 555 111."

Earlier this week, an elderly man was assaulted outside a Christchurch supermarket.

The alleged attacker had to be dragged off his victim outside New World St Martins on Tuesday.

A 23-year-old has been charged with common assault and is due to appear in court on Monday.