Ma'afu crashed over early in the second half to give Saints their fourth try. It was the his first score in black, green and gold - the 31st player to score a try for the first team this season - and capped the Australian's man-of-the-match performance.
There were four ovations for the former Wallaby, one for the try, two when he came off the field (the first when he was replaced by Gareth Denman, the second after a brief late cameo while Alex Waller was in the sin bin), and another when he was announced as the man of the match.
"I loved the reception from the fans," he told SaintsTV. "It's good to come out and play well and to get that kind of reception when you come off the field makes you want to come out and do it again next week!
"Thanks to all the supporters for that!"
Ma'afu was at the heart of a powerful performance from the home scrum, which after an even start went on to dominate the Irish eight.
"The first few didn't get our way but we stuck to the plan and towards the end we got the momentum going," the tight head prop added. "We worked hard as a unit and are happy with it."
Saints got off to a great start, Jamie Elliott crossing with 13 minutes on the clock. The winger went over for a second late in the first half, with Kahn Fotuali'i also crossing.
Ma'afu's try secured the bonus point two minutes after the break, and at 29-0 Saints were in the driving seat.
But three tries in quick succession from London Irish just past the hour put the capacity crowd on the edge of their seat, and it was not until Waller redeemed his earlier sin binning with an 80th minute score that breathing space was achieved once more.
So while Ma'afu said that the maximum haul was a satisfactory result, especially given that it confirmed the club's place in a fifth successive Aviva Premiership semi-final, there will be plenty to work on during the week.
"We're happy with the five points and we'll take that," he said. "But that part of the game [around the hour] is something we'll look at and improve on in the coming weeks.
"We had a good start. It's something we look to do every week and we'll take a lot of confidence from that leading into next week."
The big matches keep on coming at Franklin's Gardens, with the Saints hosting Harlequins in the Amlin Challenge Cup semi-final on Friday night.