The Duchess of Cambridge was the centre of attention as thousands watched members of the Royal Family attend Church on the Queen’s Sandringham estate on Christmas Day.

Police estimated that 3,000 people gathered outside the church and royal-watchers said scenes were reminiscent of the “Diana days”.

The Duchess was spending her first Christmas as part of the Royal Family following her marriage to Prince William, now the Duke of Cambridge, in April.

By 9.30 a.m. hundreds were waiting at the gates, with queues stretching back around 300 yards.

And the Duchess, with the Duke at her side, spent 20 minutes greeting well-wishers after leaving the service.

Veteran royal-watcher Mary Relph, 77, from Shouldham, near Sandringham, said the royals had been spending Christmas at Sandringham for the last two decades and queues have never been as long.

“I have never seen queues like this on Christmas Day before, I have never seen this amount of people here since Diana was alive,” she said.

“People obviously came to see Kate Middleton. And she was fantastic.”

Journalist Alison Croose said she had not seen such large Christmas Day crowds at Sandringham for years. “I agree with Mary, I have not seen crowds like this since back into the Diana days,” said Ms Croose, a former royal correspondent with Norwich-based regional newspaper the Eastern Daily Press.

“It reminded me of the Diana years – when Diana introduced Prince William to the crowds when he was about seven or eight.

“It was touching. Diana used to have her hand on his back. Now you see Prince William with his hand on the Duchess’s back. It was really nice.”

Ms Croose said there was also an unusually large number of royals at the service.

Onlookers said the Duchess seemed to be enjoying herself.

“She looked very relaxed with the crowds and very relaxed with Prince William,” said Cath Davies of Cardiff. “She was confident but not over-confident. She seemed to be enjoying herself.”

The Duchess wore a plum-coloured coat and hat.

A Buckingham Palace spokesman said she was wearing a hat by Jane Corbett.

Her coat was created by an independent British dressmaker, he added, but he declined to reveal the designer’s identity.

“The Duchess is keen to use independent British dressmakers, whose skills and craftsmanship she admires,” he said.

Ms Corbett, who is based in Hungerford, Berkshire, describes herself as a “couture milliner and artist” on her website.