Special royal birthday for one in Adelaide

It was a royal visit focused on the young, but the Duke and Duchess of Cambridge also made time for the young at heart during their stopover near Adelaide.

At the end of their two-and-a-half hour visit to Elizabeth, north of Adelaide, Kate and William took a moment to make 100-year-old Monica Swarbrick's day.

"The duke wished me a happy birthday," said Ms Swarbrick.

On a hot and sunny Wednesday in Elizabeth, Kate wore a dusty pink Alexander McQueen outfit, while William was in a navy suit and maroon tie.

Ann Hargreaves, 87, was one of the lucky few to speak with the duchess outside the civic centre.

"She (the duchess) said 'it's a lot warmer here than it is in England'," Ms Hargreaves, who was born in London the same year as the Queen, told reporters.

Maurice McCartney, 73, shared a moment with William as he greeted wellwishers.

"I said 'it's fantastic to meet you, and he said 'I've got to keep moving'," said Mr McCartney, who was sporting a Digger's slouch hat and a woollen Union Jack scarf.

On the youth-themed Adelaide stop, William and Kate visited a community music program and a nearby skateboard park, before heading to the Playford Civic Centre for their last engagement - an official reception with around 200 guests all aged under 30.

The royal pair were met with wild applause from thousands of fans lining Playford Avenue when they stepped out of the royal motorcade, about 12.30pm.

After unveiling a plaque renaming the forecourt of the civic centre Prince George Plaza - after their nine-month-old son - William and Kate entered the reception.

The couple split up inside to mingle with with local volunteers and students.

Maria Hull, 18, from Northern Connections community group, said the duke told her he had "played a didgeridoo before".

"He actually owns it, he has it at home," Ms Hull, from Salisbury, said.

"He said he really appreciates Aboriginal culture."

Zoe Stone, 23, was one of a group of volunteers from cancer support group Canteen to meet the duchess.

"I'm shaking after getting that opportunity to meet her," Ms Stone told AAP.

"I was nervous, but she was very lovely and she was very supportive of the organisation."