All smiles as Britain's William and Kate meet Pakistan PM Khan

Britain's Prince William (right), Duke of Cambridge, and his wife Kate arrived in an auto-rickshaw for a reception in Islamabad. (AFP/Aamir QURESHI)

The Duke and Duchess of Cambridge were greeted with handshakes by a smiling Khan, who first met William when the prince was a young boy, on the steps at the prime minister's house in the capital.

Pakistani media simultaneously aired archive images of Diana with Khan - then a World Cup-winning cricketer who had just launched his political career - during her own visits to Pakistan more than 20 years ago.

During the meeting with the royals, Khan recalled "the love and affection among the people of Pakistan for Princess Diana" thanks to her support for charitable causes, according to a statement released by his office.

Kate wore a traditional Pakistani dress in vibrant green and white with a dark green dupatta, or long scarf, draped over her shoulder - a change from earlier in the day when she was dressed in a royal blue shalwar kameez, the traditional Pakistani long shirt with trousers.

But the Duke opted for Western attire again - a dark suit and tie.

The couple lunched with Khan before he headed to Saudi Arabia on Tuesday afternoon, where he is expected to continue his mission to help defuse tensions in the Gulf by facilitating talks between Riyadh and Tehran.

It came after a busy morning for Kate and William, the first British royals to come to Pakistan since William's father Charles visited with his wife Camilla in 2006.

The couple launched their five-day tour of the deeply patriarchal South Asian country by signalling their support for women's education with a visit to a girls' school in Islamabad.

They dropped in on a mathematics class, where televised images showed them sitting with some of the young students, whose blue uniforms matched the Duchess's dress.

A video tweeted by a British reporter accompanying the couple showed William smiling as he was told the girls were "big fans" of his mother, who died in a car crash in 1997.

"That's very sweet of you," he could be heard saying in the video. "I was a big fan of my mother too."

TIGHT SECURITY

William and Kate spent roughly half an hour at the government-run school before they were waved off by smiling students.

They were whisked away under heavy security to visit the Margallas, the Himalayan foothills that nestle Islamabad, where they could be seen walking with conservationists in the sun.

Kensington palace said they worked with more children from local schools to set up a leopard camera trap in the hills.

William and Kate also met President Arif Alvi, and attended an evening reception where the couple arrived in a colourful rickshaw at the foot of the Pakistani national monument.

At the reception, William donned a traditional South Asian dark-green sherwani, while Kate wore a green sequined evening gown with a matching scarf.

"The UK and Pakistan share unique bonds and so it will always be in our best interests for you to succeed," William told the reception.

"You can rely on us to keep playing an important role as a key partner and your friend."

Security is extremely tight for the five-day trip, during which the couple is set to visit Pakistan's second-largest city Lahore - once the capital of the Mughal Empire - as well as the mountainous north and the region near the border with Afghanistan in the west.

Meeting young people and promoting education is one of their priorities for the trip, Kensington Palace has said. Nearly half of Pakistani school-age children - 23 million - do not attend school, UNICEF says.

Girls are particularly sidelined from education in a country where women have struggled for basic rights for decades.

For many in Pakistan, nostalgia for Diana has lain heavily over the trip.

She first charmed Pakistanis with an official visit in 1991, and is remembered fondly for her efforts on later private visits to help Khan raise money for a charity cancer hospital.