Her warning could not possibly have been any clearer.

"If anyone tries to celebrate it with me, they can have another think about it," Dame Kate Harcourt had warned ahead of her 90th birthday.

It seems - this time, at least - nobody listened to the Dame.

KEVIN STENT/FAIRFAX NZ

Dame Kate Harcourt at her home in Wellington (file photo).

During rehearsals on Friday - yes, she is rehearsing for a new show on her 90th birthday - Harcourt was whisked away for "publicity" photos while the cast and crew gathered in the green room at Circa Theatre in Wellington to set up for a surprise.

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There was nervous muttering about how Dame Kate would take it.

ROBERT KITCHIN/FAIRFAX NZ

Actor Dame Kate Harcourt (centre) got a surprise from her fellow thespians at Circa, when they held an impromptu surprise party to celebrate her 90th birthday on Friday.

Everyone believed she was physically up to it. But, then again, she had made that warning.

Publicist Colleen McColl - who had invited Stuff along to witness what could turn into a complete disaster - arguably stood the most to lose but even the stage manager looked anxious as he rearranged the cheese wheel, crackers, and grapes.

There was, in the end, no need to worry as Harcourt walked in. As Happy Birthday rung from the second floor of Circa Theatre in Wellington it was clear nobody was getting told off.

She leaned lightly on her walking stick, mouth agape. She was clearly quite chuffed. 

How did she feel about it all?

"Awful," she said, though the laughter suggested it was not so bad.

"It is a terrible milestone to make... never mind, I will do my best to enjoy it."

Harcourt was already well past New Zealand's retirement age when Molly Weaver - who,  aged 20, is the youngest in the cast of Destination Beehive: 2017 - was born.

For Weaver, on her first big show, acting with New Zealand theatre royalty had been made easy.

"It's just like hanging out with a friend," she said.

Though, it should be pointed out, this is one of those friends who inadvertently shows the younger one up: "She is way better at remembering [lines]."

Director Jan Bolwell saw her eldest cast member as a role model in an "ageist society".

"When she is here we make sure we work really constructively. She is fantastic with learning her script and learning her lines."

 - Stuff