"I must admit, I was thinking 'I'm going to play Dame Susan Devoy, world champion, this is going to be a nightmare'.
"Then I saw how [Prince] Harry took on Usain Bolt."
Mr Key barely broke a sweat in his salmon business shirt and suit pants, while Dame Susan stepped out of her high heels for the friendly match.
The two played briefly in front of a crowd of onlookers, which included children from St Mary's Catholic School and Tauranga Boys' College.
Dame Susan said she tried for a long time to get Mr Key on board but the Christchurch earthquake, Rena, Rugby World Cup 2011 and the general elections got in the way. Eventually he responded with a text saying he would be there.
"We really wanted him to be here. What better than to have the Prime Minister in your place? That's quite important to us," Dame Susan said.
Dame Susan said she was honoured to have her name on the building "but this is the culmination of a long, long project, so for all of us this is a dream come true".
Centre manager Karl Brown said they had already signed up more than 100 new members.
"It has been huge. It's wonderful. I think it's because it's a new facility and having something new is always attractive.
"We are attracting more families."
Mr Brown said he and members of a relocation committee spent "thousands of hours" trying to get the centre up and running and, now it had arrived, he was looking forward to having barbecues on the deck with members and their families.
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