A pensioner living in Canada has taken out a newspaper advert to apologise to the Jewish boy he punched when he was growing up in the 1950s.

Tom Caldwell, who grew up in Toronto but whose family were Protestants from Northern Ireland, said he would more regularly hit Catholics, but hitting Howard Rosen has “always bugged” him, because he knew it was anti-Semitic.

Now, ex-boxer and grandfather-of-four Caldwell has decided to lay the 65-year demon to rest by apologising publicly, and took an advert out in the Canadian Jewish News, reading: “To Howard Rosen, sorry I punched you at Runnymede Public School in the early 1950’s. Tom Caldwell.”

He later told Buzzfeed: “In the west end [of Toronto] there were not a lot of Jewish families, and not many Jewish kids at Runnymede… The thing that bugged me is that in the back of my mind I knew it was an anti-Semitic thing. I used to box and I punched lots of guys. I’m from Northern Ireland and I was probably more likely to punch a Catholic in those days — but this bugged me.”

Caldwell has no idea whether Rosen is still alive, but said that if he got in touch, the former assailant would offer to buy his past victim lunch. “Maybe it’s an encouragement for people who have been subjected to that, at whatever age, that sometimes people can change.”