"You have learned not just about reading, but you have learned about yourselves," he said, hoping the men's achievements would be an inspiration to others. "Nearly 1 million New Zealanders struggle to read," he said.
"Not being able to read is like a padlock for your opportunity. Finishing it gives you a hold of the key."
Among those present was former Governor-General Dame Cath Tizard, who as patron of the New Zealand Howard League said she was one Governor-General who had been in a prison.
Others included league president Tony Gibbs, chief executive Mike Williams, major sponsor Rebecca Turner, strong supporter Lady Deborah Holmes, and tutors of the three men. Mr Gibbs said the league has 300 voluntary tutors throughout the country, with projects in the 15 prisons. He said it was an honour to have the Governor-General acknowledge "what we've been doing for some years now".
"But," he told the men, "this is your day, this is your achievement. I want you to be proud."
Each spoke briefly, thanking their tutors, while Mr Gibbs thanked Mr Massingham, noting a claim that Hawke's Bay Prison has more graduates than any other prison. The Governor-General said his visit was "fulfilment of a promise" he made to the Howard League, and it was rewarded in seeing the men receive their certificates.
"If it means a lot to them, it means a lot to us," he said. "A lot of people are here [in prison] because they can't read."