More than 400 firearms were found in the home of Wyverstone Parish Council chairman James Arnold last year.
He was due to face firearms charges but died of cancer, aged 49, in July 2014.
Anthony Buckland, 65, from Stoke Holy Cross, Norfolk, is on trial at Norwich Crown Court and denies selling prohibited weapons.
He also denies fraud by false representation.
Prosecutor Andrew Oliver told the court the discovery in Wyverstone, near Stowmarket, was the "biggest stash of weapons this country had ever experienced".
Opening the case last week, Mr Oliver said firearms including air rifles, pistols, handguns, shotguns and automatic machine guns were found in a secret room in Mr Arnold's house.
The room was accessed through a hidden door in his kitchen.
Officers also found a safe behind a false wall.
No explanation of why Mr Arnold amassed the arms has been offered to the jury.
Mr Buckland told the court he had known Mr Arnold for more than 25 years.
He said he had legally supplied him with guns and ammunition but would never have procured illegal firearms.
Asked about news coverage of the find, Mr Buckland said he had been "glued to the television" but had not been worried about his involvement.
"There is no link to me because I had never supplied Arnold with anything illegal," he added. "I didn't start to panic whatsoever."
The court learned Mr Buckland supplied 26 weapons to a man called JJ Hambrose, 16 of which were found at Mr Arnold's home.
The prosecution has claimed Hambrose was a fictitious character.
But Mr Buckland insisted Hambrose was a genuine customer he had known since the 1980s.
He denies 20 counts, some of which relate to Mr Arnold and some to other customers.
He had converted many of the weapons, supposedly to make them legal, but the court has heard such a conversion was not technically possible.
The trial continues.
Photographs seen in court have revealed how a hidden door and false wall in a Suffolk house masked the biggest stash of illegal weapons found in the UK.