The former St Ignatius College Riverview classmates "had a great night" with 88 friends at Kirribilli House, the official Sydney residence of the Prime Minister.

"We all knew Tony had lost the Prime Minister's job to Malcolm Turnbull and that he must have been disappointed," Mr Anderson said.

"But politics wasn't mentioned at all. The night was all about the school reunion.

"Tony looked very relaxed and after a traumatic week I think he was pleased to spend time with mates and enjoy himself."

Mr Anderson said the Old Ignatians were bussed to Kirribilli House from a North Sydney hotel.

Mr Abbott stood at the front door and welcomed each guest warmly.

"Tony was a great host and we felt quite honoured to be celebrating in such a significant venue," Mr Anderson said.

"We were also happy to be raising money for the Jesuit Mission in India.

"The reunion was 100 per cent funded by the people attending the event. There was never any suggestion of the taxpayer footing any part of the bill."

Mr Anderson and Mr Abbott sat next to each other during most of their classes from years 7 to 12.

They graduated together in 1975 in a group of 105 students

"Things were mostly done alphabetically at our school and Anderson came after Abbott," Mr Anderson said.

"Tony was a day boy and I was a boarder. The class of 1975 was a pretty big group and a lot of our classmates went on to become notable."

Other famous classmates included Macquarie Bank head Nick Moore and Ignatius Jones (Juan Ignacio Trapaga) who sang in the shock rock band Jimmy and the Boys and went on to become an actor, journalist and events director.

After leaving St Ignatius, Mr Anderson and Mr Abbott attended Sydney University at the same time.

"I had a lot to do with Tony at college," Mr Anderson said.

"Tony was smart at school and university and went on to become a Rhodes Scholar.

"He was a good sportsman and an easy going, friendly fellow.

"Tony was on the student council at university and always had a strong interest in politics. I wasn't surprised at all when he became Prime Minister.

"Everyone at the reunion was proud of Tony's achievements but they were just of proud of other classmates who went on to become international journalists, cameramen, lawyers, farmers, flight attendants, bankers and businessmen.

"Three of the guys at the reunion went through pharmacy with me at university.

"Peter Sullivan, a mate who lives in Sydney, did a great job tracking down former students who are now living and working all over the world. It was a huge job."

Other western region residents at the reunion included Jim Hedger (Dubbo), Robert Montgomery (Nevertire), Geoff McKay (Warren), Michael Kenny (Gilgandra) and James Renshaw (Mendooran).

"Some of the guys we normally never see because they live so far away," Mr Anderson said.

"Five out of 105 students have died and I think everyone in attendance felt pleased to be alive and able to share the stories of what we have been doing for the past 40 years.

"There were people from all walks of life and political persuasions. We all talked to each other in a very non-political way. We wanted to take advantage of the opportunity to reconnect with each other.

"On a personal level, I felt disappointed for Tony because politics is such an ugly game that so often ends in tears.

"But he handled himself well on the night and will now have more time to spend with family and friends."

Mr Anderson said attending St Ignatius College had been a tradition for his family.

"My son, Louis, graduated in 2014, 101 years after his great-grandfather Luke McAlary," he said.