"I experienced my first hongi there," he said.
"I met a young man who has come from a place where he has struggled and I feel very privileged that he was willing to greet me like that."
Empowering youth to reach their full potential is what drives him, he says, and it's what motivated him to join the YMCA as a volunteer 37 years ago.
"I am chair of our local branch in Derbyshire and I love to keep in touch with the young people in my own community."
Mr Posner was made an Officer of the Order of the British Empire in 2013 for his services to the YMCA and was elected world president the following year.
He divides his time between England,the YMCA headquarters in Geneva, Switzerland, and travelling to visit some of the 1200 YMCA centres in 119 countries.
"This is my first visit to New Zealand and it is even better than I expected," he said.
"I've met a lot of English people who have been here and they have all said it is a wonderful place filled with nice people.
"On this short visit I have seen that it is true and I want to come back for a holiday with my wife next year."
Mr Posner's term as president will end in September, when his replacement will be elected from a list of nominated candidates.
The YMCA, or Young Men's Christian Association, was founded by philanthropist George Williams in London in 1844 and was based on developing "body, mind, and spirit".
Mr Posner said those principles have not changed and although the organisation works with people of all ages, youth are still the main focus.
YMCA Whanganui will soon welcome Aaron Palmer as its new chief executive.
Whanganui-born Mr Palmer has been living and working overseas and is about to return with his young family to live in his home town.